Evening star., 1898-01-26
SELECT A DESIGN
Estimate for Constructing Viaduct
Over Rock Creek.
GEORGE s. MORISON'S PLAN CHOSEN
Commissioners Formally Refer the
Matter to Congress.
TEXT OF THEIR LETTER

The act Of March 3, 1897, making appro-
priation for the expenses for the District of
Columbia for the fiscal year ending June
so, 1898, and for other purposes, contained
the following provision:
''The Commissioners of the District OF
Columbia are hereby authorized to secure
designs, by competition, for a bridge or via
duct across Rock creek on the line of the
extension of Connecticut avenue, and the
sum of $1,000 Is appropriated therefor
Under this authority a survey Of the site
of the proposed structure was made and a
plan and profile prepared, showing in de-
tail the physical features of the ground
and the streets. avenues. roads and struc-
lures in its vicinity. as we'll as the general
elevation Of the profile Of the rock under
lying the axis Of the proposed bridge, as
determined by borings and test pits sunk
for this purpose. Copies of these maps and
profiles were furnished as exhibits to a cir
cular letter addressed by the District Com
missioners to three prominent bridge en-
gineers, Messrs Geo. 8. Morrison IS Wall
street, New York city: L. L. Buck, 46 21st
street, New York city, and w. H. Brett
haupt, 35 Nassau street. New York city.
In response to this letter, each of the
gentlemen named agreed to participate In
the competition, and there were received
five separate designs of distinct kinds,
each fully detailed and all exhibiting great
ability and care in their preparation.
The Submitted Estimates.
In order to compare these designs prop
erly and to arrange them in their order Of
suitability. as provided in the letter of
instruction to competitors. a review OF
their submitted estimates of cost was pre-
pared. the result of which will appear in
the following estimates as modified for
comparative purposes:
Exhibit B-Sheet No. 1, masonry, 81, ,OS9,-
900 in granite. $903 900 in sandstone, $685.
600 in concrete; sheet No. 10. modification
sandstone, $500. $50 in concrete.
Exhibit C-Sheet No. 8, melan, $S59, 200 in
granite, $725. 1872 in concrete; sheet No. l..
steel, 1914, 1856 in granite.
steel, $509,O0O in sandstone, $5O3, 72S In con-
crete; sheet design y, steel $437, ,74S in
sandstone.
The Judgment of the Commissioners was
unanimous in fixing the order of merit
and suitability as follows, the competitors
being rated on the basis of the best de-
sign submitted by each: First, design Of
George 8. Morrison. marked Exhibit b.
exhibit c." third, design ], Of w. H..
Breithaupt, marked Exhibit D."
General Review of Design.
In accordance with this decision, the fol-
lowing general review Of the design pre-
ferred by the Commissioners vas today
submitted to Congress:
This design contemplates masonry
viaduct of full centered arches of a total
length between abutments of 1,341 feet. The
arches are nine in number, five Of which
have spans of 15O feet and four have spans
of 80 feet. The piers between the arches
are each 20 feet, thick except in two cases
where an S2-foot arch adjons a 15O-foot
arch, at which places the thickness Of the
piers Is increased to 81 feet. These last
are true abutment piers, the remaining
piers being designed simply as intermediate
supporting piers. The piers and abutmcnts
rest upon foundations carried to the solid
rock, which it is proposed to prepare prop
erly by stepping off and leveling up, for
the loads to be brought upon it.
"a conspicuous and characteristic fea-
ture of the design is the construction Of a
series of subordinate arches piercing the
resting upon them and on their launches
This substitution for the usual full cpan-
drel facing has very pleasing effect OF
| lightness and Is of material advantage
economically. Above these main and span.
drel arches is a leveling bed of concrete
on which Is placed a uniform depth OF
about three feet of gravel supporting ar
asphalt roadway pavement Of the stand.
| ard type laid in this city; within the body
| of this gravel provision can be made, as ir
| an ordinary street, for subway construc
| ton as may be desired, such as electric
| subways, gas and water mains, &c.
Sidewalks ON Brackets.
'"The masonry arch construction just de
| scribed has width transversed to thu
axis of the bridge of but two feet greater
than the proposed asphalt roadway, ant
| the design contemplates the carrying O.
the proposed sidewalks each ten fee
wide, on brackets projecting at interval.
| Of about II feet, and secured to the ma
| sonry, and by connections entirely acros.
| the bridge to the opposite brackets, in {
most substantial manner with ample pro
| visions for stability. These brackets pro
/ ject about nine feet and are to be made Of
cast iron and prepared so as to simulate
the mssonry to which they are attached
From the points of view from which alone
they are visible. or indeed from close in
| spection, they will appear as masonry. ani
their proposed use is a provision of erea1
| economic value.
Upon them will rest suitable con-
struction of structural steel, supporting a
| flag or granolithic foot walk and a railing