SHEPPERD'S DELL BRIDGE
(YOUNG CREEK BRIDGE)
|Shepperd's Dell Bridge ca.
||Shepperd's Dell Bridge ca.
Spanning Young Creek on the Columbia River Highway in Shepperd's
Dell State Park, Latourell vicinity, Multnomah County, Oregon.
Date of Construction:
Reinforced-concrete deck arch.
Samuel C. Lancaster, Consulting Engineer/Assistant Highway
Engineer, K.P. Billner, Designer.
Pacific Bridge Company, Portland, Oregon.
Oregon Department of Transportation.
Vehicular and pedestrian bridge.
Shepperd's Dell Bridge was designed by bridge designer K.P.
Billner under the supervision of Samuel Lancaster in 1914.
The bridge is a reinforced concrete deck arch with a 100-foot
span. It was the second bridge built on the Historic Columbia
River Highway. The solid curtain wall between spandrels and
above the crown of the parabolic arch is a unique feature
of this bridge. Later bridges of Conde B. McCullough's on
the Columbia River Highway imitate this design. K.P. Billner
believed this was one of the strongest and best-erected bridges
on the highway. The structure harmonizes beautifully with
its hilly woodland setting.
Shepperd's Dell is located on the Columbia
River Highway just west of the community of Bridal Veil. This
charming and picturesque: spot was presented to the public
in May, 1915, by George Shepperd, as a memorial to his wife.
George Shepperd gave these eleven acres as a public park,
because he loved it and came here with his family to be refreshed
when they were denied the privileges of church and Sunday
school, because there was no road.
K.P. Billner paid tribute to George Shepperd
when he wrote: ''Men of Wealth and high position have done
big things for the Columbia River Highway which will live
in history; but George Shepperd, the man of small means, did
his part full well. The bridge complements the enchanting
landscape found in this area of the highway.
DESIGN AND DESCRIPTION
This bridge is a graceful reinforced concrete
deck arch and was the second bridge constructed by the new
highway department on the Columbia River Highway. The main
arch spans 100' and consists of two parabolic arch ribs. Four
spandrel columns balance each side of the arch and terminate
in half circle curtain wall. The spandrel columns have a decorative
feature at the junction point of column and arch, which is
a simple capital form. Above the parabolic arch there is a
solid spandrel wall, which closes the space between the spandrel
columns. The spandrels are reinforced to make them act as
girders, and are capable of sustaining the bending moment
over half the span. The spandrels distribute the loading on
the arches. The influence of stiffening of the spandrels was
not considered in determining the dimensions of the arch ribs!
The girders composing the spandrels are heavily reinforced
and designed to distribute the stresses due to moving loads,
therefore increasing the rigidity of the structure. Calculations
for decking, loading thickness of floor beams and their spacing
are the same as Latourel Bridge. The total width, including
railings, is 25'. Each walkway is 3'-3" in width, while
the roadway between curbs measures 169'-10''. Angle iron reinforcement
is evident on the edge of the curbs.
This is one of eight deck arches built
between 1913-1921 on the Columbia River Highway in Oregon
between Troutdale and The Dalles. It is the third largest
of the single arches, after Moffett Creek and Mosier Creek.
By 1910 bridge construction was moving
away from massive construction and towards the flattened parabolic
curves with narrow ribs, slender spandrel posts, and minimal
piers that scientific reinforcing was to make possible. Such
European innovation like the light slabs of Maillart and the
thin-walled box girders of Freyssinet were slow to appear
in the United States. It was the engineers of the Oregon State
Highway Department, who played a leading role in the development
of American concrete bridges. Their earliest contributions
were the bridges along the Columbia River Highway. Bridge
designer K.P. Billner attempted innovative and creative designs
with his bridges on the Columbia River Highway, and this bridge
is an outstanding example of his early work in Oregon.
The bridge abutments are anchored to solid
which helped to cut down on construction costs. Billner explained:
From past experience with the bridges already
constructed I have learned that the principal opportunity
for saving is in the abutments. This savings can be accomplished
by a careful preliminary examination of the bridge site. I
will endeavor, in my designs, to as far as possible cut out
the concrete abutments and let the solid rock ledges serve
in the place of thy concrete.
This bridge, like the Lateral Creek Bridge,
is characteristic of this cost saving principle.
K.P. Billner approved the following specifications
for the form work by The Pacific Bridge Company:
The deck we would like to use 1" shiplap
supported by joists on 2" centers. Joists to be 2 ''x
10 '', 2'' x 12'', 3'' x 8'' or 3'' x 10''. The stresses will
not exceed 1000 # per sq. in.; and we think you need have
no fear of any of the joists breaking as they did on the viaduct.
The 1" material will certainly carry a 10-1/2 slab for
a 2' spacing of joists without noticeable deflection. We will
have a longitudinal cap under every cross girder and a longitudinal
stringer under the sidewalk girder bracketed out from the
main form, and tied with bolts thereto, so that there will
be no possibility of deflection of these parts. The form for
the sidewalk girder will be of 2' material and every effort
will be made to secure perfect alignment of 2'x 4' studs 21"
on centers, these in turn to be kept in line by 4''x 4'' wales,
and the whole form arches, as the Construction Co. has nearly
all the 1 -inch material on the ground and the cost of same
is very great. We do not like to take any chances up in the
air for our own safety, and would like to use sufficient wales
and sires so that absolutely nothing can happen which would
permit the walls to go out of line in any way.
These specifications for falsework clarify
the contractors desire to erect a first class structure that
would not give in to the stresses of the concrete. They help
to explain the method of false work construction before plywood
increased in popularity and replaced the common shiplap lumber,
which is now obsolete.; An August 6, 1914 letter from Billner
to Lancaster states: ''It is my opinion that the falsework
for the Shepherd's Dell Bridge is the strongest and best erected
of all built on the Columbia highway's The weekly Engineer's
Report of May 3, 1914 reveals that the process of cutting
out footings for the Shepperd's Dell Bridge was slow because
of the careful falsework construction and the dangerously
steep conditions at the site.
This bridge has precast concrete balustrades
with arched openings, caps and posts identical to those on
Latourell Creek Bridge and other Columbia River Highway bridges.
Topping the balustrades is a cast-in-place concrete cap and
support brackets. The curved brackets below the deck terminate
in a triangular motif above the spandrel columns. Basalt piers
with concrete caps are found at each end of the bridge railings.
At the west end of the bridge a basalt guard wall, which is
a series of arches with cast concrete caps abuts the basalt
pier at the northwest corner of the bridge.
Shepperd's Dell Bridge is a conventional
reinforced concrete arch bridge. The arch ribs are set more
to the outside of the raceway than others. The spandrel columns
are replaced by a longitudinal wall at the crown, unlike some
arch bridges where the separation at rib and eck is maintained
throughout. It is an elegant small bridge with an air of permanence
that is most agreeable.
A stairway and winding trail to the waterfalls
originates at the southeast end of the bridge. The unusual
cast-in-place railing on this stairway is a unique example
of thin reinforced concrete construction techniques. Its sharp-angled
design contrasts with the traditional balustrade form of the
On August 5, 1915 Roadmaster John B. Yeon
notified contractors that they were not to cut any of the
shrubbery or cut into the County's right-of-way without explicit
instructions from the County Highway Engineer. ''Actions of
this kind ruin the looks of this road and cannot continue.
We have exercised the greatest of care and incurred great
expense in finishing out slopes on the Columbia River Highway,
so that every one driving over same may appreciate and enjoy
the beauty of the construction, as this Highway is in a case
of its own and is not an every day County Road. It is a Highway
that will be shown to the whole world and l wish to have your
heartiest cooperation in the above suggestion. Vegetation
management is a current issue at this bridge site much of
the bridge is hidden by the tall tree canopy.
REPAIR AND MAINTENANCE
Maintenance records for this bridge indicate
that in the 1930s repairs were necessary to the curbs, handrails
and spindles. Heavy moss growth was evident so the bridge
was cleaned and painted with a coat of atlas cement. In 1937
there was evidence of spindle stalling. Between 1940 and 1969
little maintenance was performed on the bridge. By 1969 ninety
five percent of the spindles in the railings were deteriorated
with the reinforcing bar exposed. A solid concrete wall replacement
was suggested to replace the spindles on this bridge. In the
late 1980s the original spindles were replaced with identical
reproductions. In the summer of 1990 an analysis of other
''Columbia River highway bridges of the same vintage revealed
similar spindle deterioration which suggests that the reinforcing
bar was located too close to the surface of the concrete.
Excerpted from Historic American Engineering Record, Shepperds
Dell Bridge (Young Creek Bridge), HAER 0R-OR-23.
Researched and written by Kenneth J. Guzowski,
HAER Historian, 1990. Edited and transmitted by Lola Bennett,
HAER Historian, 1992