Harrisburg telegraph. [volume] (Harrisburg, Pa.) 1879-1948, 1915-09-23
BUILDING A DAM
ON SINKING SAND
A RIVERS STORY
Construction of Susquehanna
Obstruction at Dock Street
Marvel of Engineering
SOME DENTAL" WORK
Quick-Sands Bridged by Use of
Floating" Foundations of
Concrete For Piers
SOME DENTAL" WORK


Were down three feet below the
foundation level now, Cowden." said
one of the men TO the Inspector. And
we amt touched bottom yet"
The drill plunged again. Down,
down another two feet or so through
the yielding bottom of the river went
the steel rod.
No use, we can't reach anything =
finally reported a dripping workman
Df the fiat. We've hit a bed of
quicksand!"
That, in brief is the story of one
of the stiffest engineering problems
the board of Public Works had to
face-and solve-in the construction
of the great river-wide hollow con-
crete dam across the Susquehanna at
Dock street II is another one of the
big public improvements that has
helped place Harrisburg on the map
of the world. Incidentally it's another
reason why Harrisburg is planning to
celebrate tbs week-and setting aside
three days to do it.
The First Big Improvement
The river dam although only now
in course of final completion was one
of the first big improvements Harris
burg planned for when II first awoke
from its civic snooze in 1901. That
was the year that the city decided to
do something big and when the people
quit authorizing the floating of inn
provement loans that time, some
ninety thousands more than a mill
lion dollars had been provided for.
True. $4,000 went toward the con-
struction of filter plant, sS65, 900 for
the extension of the sewers, S250,000
for creating a park system, 100000
for paving street intersections and
SIS, 900 was set aside for the dam.
The PURPOSE
The purpose originally was to back
the water sufficiently to cover the
mouths of the sewer outlets along the
river. The construction of the inter-
ceptor however eliminated this
nuisance so far as accumulation of
filth in the low water was concerned,
but the building of the wall and steps
presented another equally serious
problem that had to be solved after
all. The solution was reached through
the medium of the dam. This was to
back the stream up to a sufficient
depth to cover the low and exposed
ground along the river shores on the
outside of the wall. So in 1913 the
big job was begun.
Frank N. Skene, of New York got
the contract His bid was S51,7S0.
although the "eXtras" growing out of
the difficulties incident to the bridg-
ing of the quicksands ran the bill up
to about $4,000. Council recently
provided some $4,000 additional to
finish the big work
New Type of Construction
Just a word about the character OF
the dam. It is unique for this section
of the country and its construction
was watched with unusual interest by
engineers. How the great 33OO-foot
long obstruction will serve the pur-
pose for which ii is intended, will be
watched with scarcely less interest.
Instead of a solid breast work the
dam is built with a sloping face, curv-
ing over concave top. The dam in
fact is merely a thick, solid shell of
concrete. The system of construction
was we'll worth watching. Sectional
forms of frame were sunk at 10-foot
distances on the foundation rock Of
the river. Upon these. piers were built.
The Pier Bases
The base for each pier was concrete,
laid on the cleared rock floor of the
river and through this bed or base,
great bars of serrated reinforced steel
was driven to a depth of four feet
The moulds for the piers were placed
over this base and when the piers
finally settled the extra durability of
the reinforced steel was assured. All
told the drilling into live rock totaled
some 1000 feet. Between the piers,
great one-ton slabs of concrete were
laid in grooves. The first slab was
placed at the toe" of the breastwork
and fitted snugly in position. On top
of this slab, was placed another; atop
of that another, and so on until the
concave arch was reached single
curved piece of concrete finished this
off No cement was used to keep the
slabs in place the big blocks of mate
rial fitted tightly in place, It's true.
but the pressure of the everlasting
tons of the waters of the Susquehanna
rolling along to the sea, held as no
cement in this world would ever hold.
on the lower side of the obstruction
F1ia
will doubtless provide mighty com
Portable quarters for the lucky lazy
fish who might want a place to loaf.
The Gray Shadow
The job went along swimmingly as
1t were, even through the extraordin-
arily deep, swift waters of the west
tern shore-"Welrs water" as 1t is
locally called.
Long strings of Golfer dams were
used and the fact that some 1900 bags
were passed into service for this
purpose alone, may suggest some idea
of the size of the job. Building the
dam across the deeper waters of the
western side of the river, was pushed
ahead with little trouble and only one
real catastrophe One day a work.
man slipped into the swirling waters
and the fact that he wore heavy rub
ber boots Offset the fact that he was
one of the best swimmers in a whole
ward of expert watermen. His body
was not picked up for days after
ward
The "Pot Holes
II was when the contractors reach
ed the stream about midway from the
city shore that the heart-breaking end
of the venture developed.
What the engineers called pot
holes" were discovered in the bed of
the stream.
Quicksands that swallowed con-
crete. foundation stones, by the tons
and yet swirled hungrily for more are
pot holes" Whereupon the section
across this stretch had to be crossed
much after the style an expert dentist
uses in swinging false tooth between
two real ones-"bridge work." they
call It.
On Sinking Sands
The excavations in the quicksands
were made as far as possible and when
after half dozen feet below the
original surface no sounding could be
reached. another Golfer dam was con-
structed and tons of stone we're dump
ed in. Upon the temporary footing
concrete was poured until solid foun-