Evening capital journal. (Salem, Or.) 1888-1893, 1890-10-14
THAT SALEM BRIDGE.
Some Vigorous Statements From a
Practical River Man.


My attention was attracted To the
appropriate article in Saturday.
JOURNAL entitled "The Salem
Bridge" Having had practical ex-
perielce in the construction of piers,
breakwaters, etc, ! WAS interested
IN the article and propose to add Il
few practical facts in connection.
First: You say the first bridge
that was carried away simply fell
down" The cause was the under
mining OF the piers, which fact can
be explained and satisfactorily
proven. The foundation of these
piers was "mistake" which the
builders and L. 5. engineer super
intending the work should have
known and avoided by considering
the material forming the bed OF the
river, and the action and force of the
| water in that and all similar locali.
| ties. The same mistake, but more
serious, is made in the foundation OF
the piers just completed. The
depth of water in the river from
Oregon City to Albany is not uni
form, but deep places" and
"shoals" or "bars" alternate, and in
a degree, regularly. These deep
places and liars may be said
to be of a permanent nature
The deep places do not ill or the
bars wash entirely away. The ban
or shoals are always of loose gravel
The deep places in The bed of the
| river is either of solid rock, clay, or
cement, or packed gravel next tu
the rock. Clay is the most perma-
nent. Cement gravel, If not dis
turbed, washes away very slowly
No loose gravel or stone, however
large, can remain or be found in the
deep places when the water is high
and has a strong current, but
always lodge on the shoals or bars.
The Salem bridge is located mid
way between two bars in about the
deepest water. the bed of he river
at this point being cement gravel.
In preparing the foundation for the
piers the contractors have driven
piles in the cement gravel breaking
and loosenlng it up for several feet
around. More piles being driven for
this than for the old piers has Of
course broken up more of the gravel
which is sure to wash out the first
high water, leaving the pier, if
standing at all, standing upon stills,
the ends of which must be split
or broomed by driving into the
solid gravel. The "Grillage,"
o-called, placed on the top of
the piles, a few inches above
the bed OF the river which is in fac,
the base of the pier leaves a space
for the water to rush through under
the pier giving it an extra chance to
wash out the gravel and undermine |
the pier. Placing the piling and |
the grillage as stated above is an
other mistake and more effectual
plan could not be devised tn con
,truct foundation that would be
to undermine. "But," says
he engineer, "we will put tons Of
'ock around that pier to prevent the
undermining, being satisfied 1t
Will undermine without the rock.
Vow we will ask the engineer II the
I'D piers being filled with concrete
we're not like solid rock aud they
we're washed down the river, how
ong will your loose rock remain at
he pier at such u time of high
water? But" says the engineer,
we will drive piles around to pre-
'ent their washing out" We will
SIX the engineer If driving the piles
o hold the loose rock will not break
Up the ground the same as the
lilies under the pier that will
wash out with the piles or let
hem spread sufficiently to let
he loose rock out and down the
iver. Taking tho water in the
iyer at the bridge as it was last
february the pressure on the bed Of
he river was about two tons TO the I
quare foot, travelling Mt the rate of
light or ten miles an hour aud
you'd wash loose ground and stone
ut Of a cavity thirteen or twenty
eet deep In the bed of the river.
Ind the pressure against the up
tream side OF the pier on stills just
omple'ed when the depth Of water
} 90 feet, will be about 800 tons.
Had those piers been placed on Z
he bed OF the river without any
oncrete foundation they would have
cen comparatively safe. but, cdriv- .
,g piles into and breaking up the
sment gravel. the foundation Of
ne piers IL ruined, sndl the only