66 
PARK AND CEMETERY. 
SUCCESSFUL CONCRETE BRIDGE BUILDING 
The Interlaken Bridge in Seattle. 
By H. L. McGillis, Chief Engineer, Seattle 
Park Commission. 
The topography of the city of Seattle is 
such that engineering problems are en- 
countered of unusual complexity and the 
construction of a bridge on Interlaken 
boulevard, over Twenty-sixth avenue N., 
is an example. 
In the platting of adjacent property a 
contour study was made and streets were 
laid out on curved lines to fit the ground 
and Twenty-fifth avenue N. followed a 
ravine on a compound curve. 
In building Interlaken boulevard a cross- 
ing was made over Twenty-sixth avenue N. 
on a very artistic and substantial rustic 
bridge, which unfortunately was supported 
upon a central pile bent and only had ten 
feet clearance. These defects did not in- 
terfere with the little used and partially 
improved Twenty-sixth avenue N. 
Surrounding property developed into a 
high-class residential district and when the 
street was paved in 1912 the Park Board 
was confronted with the problem of re- 
moving or rebuilding its bridge. As the 
existing bridge was of a construction 
which prohibited its being raised, and on 
account of the desirability of maintaining 
traffic, coupled with the showing that great 
improvement of alignment could be gained, 
it was decided to locate the new bridge , 
alongside of the old one. 
Surveys were made and plans prepared 
for a reinforced concrete arch bridge, de- 
scribed briefly as follows : Total length of 84 
feet 4 inches, having one central arch of 41 
feet clear span, with 9-foot raise from 
springing line and end walls. Total width 
of 32 feet 8 inches, covering a 24-foot 
roadway and walk on the south side. 
The railing is of plain heavy posts and 
panels of fancy rough bricks and plain 
square openings, the result being very 
pleasing. Four of the posts were mounted 
with a single ball cast iron lamp of plain 
design. In addition to lamps on top, pro- : 
vision was made for placing a cluster of 
lamps at the center of the under side of 
the arch to light street below. 
The clearance under the arch is 15 feet 
6 inches and is ample for modern trucks 
and moving vans. 
The new location necessitated the chang- [ 
ing of about 1,000 feet of roadway, both 
in alignment and grades, with very satis- 
factory results. It was intended to finish i 
the concrete surface with an acid wash and ■ 
selected gravel was used with great care 
in the puddling. Upon stripping a fine 
finish was left, but acid wash was not used, I 
as it was decided to cover the bridge with 
ivy, which, with the touch of color, on the 
panels, will, no doubt, make an attractive 
appearance. 
An estimate from finished plans was pre- i 
pared, based upon the prevailing unit 
prices of similar work, and totaled $4,700. 
The Park Board’s policy and practice 
being to do practically all of its own 
construction work, Superintendent J. W. , 
Thompson was directed to build the bridge 
with crews from the regular park organi- 
zation. 
Following is a summary of actual ex- 
penditures. The item of labor is apparently 
high, due to charter provision which makes 
a minimum wage on all city work $2.75 
per day, and a special foreman was em- 
ployed at $5 per day : 
Cost of Interlaken Bridge. 
Engineering. $63.58; labor, $1,126.83; ce- ] 
ment, $899.25; sand and gravel, $779.40: 
lumber, $307.68; steel, $262.83; nails and 
wire, $25.07; lamps, $78; pipe and fittings, , 
$11.20: drain tile, $7; cartage, $18; brick, 1 
$37.80: mixer (vent), $'55; mixer (coal), j 
