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


any support from a wall to keep it in
position. Relative to this south abut-
ment, Mr.. Brown stated at our con-
ference that he had made the main
wall % feet thick at the bottom, and
that on account Of finding rock bot
tom, the height had been reduced to
80 feet, also that he had increased
the thickness Of the wing walls pro-
portionately. The main wall then
under these conditions, should have
thickness Of g feet at the bottom and
the wing walls should be the same
thickness where they join the face
wall, reducing of course further south
il the foundation rises and they may
have less weight. In view Of the le-
gal requirement to adhere to the filed
plans, it is difficult to see how changes
in the thickness of the walls could be
made. Now with regard to the design
for the wing walls noticed on the
detailed drawings that these wings are
fared, that is, being wider apart at
their rear end than where they join
their main abutment wall, also that
they step down towards the rear end.
The driveway on the bridge is I8 feet
wide with wheel and hub guards pro-
vided. 1t is customary on wagon road
bridges to construct the wing walls
masonry to the full h9ight of the APP
preaching roadway, widening the en-
bankment out SO as to fill in level be-
tween the walls and then to build
masonry parapet to 3 or 4 feet above
the road surface, thus forming a COM
plete guard to guide teams into the
bridge proper, and give proper space
for teams that may be passing each
other. On railroad bridges this is
not necessary, as all that is required
there is to preserve the proper width
of road bed for the tracks, and the
side slopes may run off either way,
the walls being built to the proper
height to retain them. In the case Of
the Bloom Ferry bridge there is no
data on the plans by which l can
work out the slopes, proper position
of wing walls, &c, at the north end of
the bridge, but at the south end
where the masonry is now built, the
thing shows for itself The total width
between wing walls where they join
the front wall is about 20 feet. Mr..
Brown advises me that there is an as
cending grade southwark of the
bridge of about foot per 100 feet,
and that the same grade extended
will reach the level of the N. & w. B.
r. r. track. IN. B.-A proper prof
lie of the bridge would show this
The result will be, the way the ma
sonry is now built, that a roadway of
not over 20 feet wide with a steep
slope on each side will form the APP
proach to the bridge from the south,
and it will be very difficult to main
tain any proper fence or guard on the
top edge of this roadway. Country
teams coming along are apt to be
timid on approaching the railroad,
and it may be difficult to handle them
and avoid accid mt especially ifa train
should be passing or standing at the
station. These wing walls should have
been built in the way and usual Gus
tom for country bridges, and with
masonry parapet or strong fence
above the road surface. This, | con-
slider serious defect in the design of
this bridge and doubt If the ap-
proaches as now designed will be sat
isfactory to the citizens of Columbia
county. 1t is further a question
whether the material composing the
embankment on the approaches will
not flow around the end of the wing
walls, down to the river bank.
If this occurs, the embankment of
the approaches is liable to be dam
aged at every food in the river. The
remedy for this latter difficulty would
be to construct additional dry mason
ry walls to hold up the slopes, which,
of course, will add just so much to
the cost Of the structure. My opinion
has been asked as to the specification
and contract for the masonry and the
quality of the work being done by
the masonry contractor. The con-
tract and specifications are in many
respects indefinite, but on the whole
call for good work. The foundations
are to be constructed, as in the opin-
ion of the engineer, may be necessary
to secure a solid bearing. The ma
sonry of wing walls of abutments is to
be third class masonry, that is, rubble-
work, otherwise the masonry is to be
rock range work, the "face stone to
be accurately jointed and bedded,
and laid in regular horizontal courses"
stones for the heart of the
wall will be the same thickness as the
face and back, we'll bedded but not