The Cambria freeman. [volume] (Ebensburg, Pa.) 1867-1938, 1889-06-14
An Inferior Dam.

JOHNSTON, June IA. NJ. yelling
ton, with +. p. Burt, associate editor
of the Engineering NetCs, of New \ ork,
has Just completed an examination OF
the dam which caused the great disas-
ter here. Mr.. Wellington states that the
dam was Ia every respect ot very interl-
OF construction and of kind wholly
unwsrIsuted by good engineering prac-
tices Of 80 years ago. Both the original
and the reconstructed dams were of
earth ouly, with no heart wall, but only
rIprspped on the slopes. The original
dam, however, was made in rammed
and watered layers which still show
distinctly in the wrecked dam. The
new end greatly added to its stability,
but it was TO all appearances simply
dumped in like an ordinary railroad fill,
or if rammed, shows no evidence o.
good'e fleet from il. Much OF the old part
is standing intact, while adjacent parts
of the new work are wholly carried off.
There was no central wall OF puddle or
masonry, either in the new or old dam.
Ii has been the invariable practice of
engineers for 80 OF 40 years to use
one or the other, # building high dams
of earth. 1t is doubtful if there is
single other dam or reservoir in any
other part OF the United States of over
80 feet high which lacks this central
wall. The reconstructed dam also
bears the mark or great Ignorance or
carelesss, being made nearlv two feet
lower in the middle than at the ends.
II should rather have crowned in the
middle, which would have concentrated
the overflow, IL it should occur. at the
ends instead OF in the center. Had the
break begun at the ends the cut of the
water would have been so gradual that
little or no harm might have resulted.
Had the dam been at once cut at the
ends when the water began running
over the center, the sudden break would
have been at least greatly diminished,
possibly prolonged, so that little harm
would have resulted.
The crest of the old dam had not been
raised in the reconstruction OF 1881.
The old overflow channel through the
rock still remains, but owing to the
crest IN the middle of the dam, only
five feet OF water in il instead of seven
feet was necessary 10 run over the cIes:,
and the rock spillway, narrow at best,
had been further contracted by close
grating 20 prevent the escape OF fish,
capped by a good sized timber, and in
some slight degree also by a trestie foot
bridge. The original discharge pipes at
| the foot of the dam had been perma-
nently closed when reconstructed, and
/ this, while a minor matter compared TO
| the other mentioned, further reduced
the possible rate of maximum discharge
| The net effect OF all these differences of
| condition was that the dam as it stood
was not much safer against excessive
| floods, apart from its inferior coLstruc~
| tion, than the original dam would have
| been with a crest only p TO feet high
/ above the bottom of the rock spiliway,
instead of feet.
1t is impossible to say If the riprap-
! ping OF the new part of the dam was as
| good as the old or not, since it has not
| been wholly carried away. 4 large
| amount of the old riprapping and slope
| wall still remains intact, aud is o. ex-
| cellent quality. 1t does not appear
| that there was any great amount of
| leakage through the dam before it
| broke. Destruction came from water
/ flowing over the top.
Mr.. Wellington said that no engineer
/ of known and good standing for such
/ work could possibly have been engaged
/ on it, since in the particulars mention
| ed 1t violated the most elementary and
/ universally unders ood requirements OF
good practice. He did not believe that
| any other dam of equal height had ever
/ teen constructed in this country wholly
| OF earth without some kind OF special
protection against leakage or abrasion
/ by water in the center OF the dam.
The estimates OF the original dam
| indicate that it was made about half
/ earth and half rock, but if so there was
/ little sviGence of it in the breaking
/ dam. The ripIapping was merely a
/ skin on each face, with more or less
| loose spauls mixed with the earth. The
I dam was - feet above water. to in
/ side slope, To l outside slope, 20 feet
/ wide on top. The rock throughout
was about l foot below the surface.
I The earth was pretty good material for
/ such dam IL il was to be built at all,
being of clayey nature, making good
| puddle. To this the fact OF its standing
intact since 1881 must be sscribed, as
no engineer of standing would have
ever tried to so construct it. The fact
that the dam was a reconstruction OF
one after over 20 years. abandonment
made il especially hard on the older
part OF shs dam to Withstand the press
of the water.