The Evening critic., 1882-03-04
THE FREE BRIDGE.
Report Of Col. Albert ON the Subject

Col 8. Il. Albert, United States Civil Engineer,
has made his report to Gen. Wright, Chief Of
Engineers, upon the modified plans OF the
Corrugated Metal Company for the construc-
tion OF the free bridge across the Potomac
River at the Three Sisters, near Georgetown,
in which he reviews the various notifications
Of their original bid with his amendments
thereto. He states that the chief foundation
for the piers, as proposed by the company,
would be inadequate to give proper strength
and security TO the structure, and recommends
that their proposition be declined, and that
the foundations be built by means of n Golfer
dam. The company also fail to conform to the
requirements in the matter Of compressive
strains on the iron.
Col. Albert makes some sensible remarks, to
the effect that the standard generally adopted
for the strength and durability of bridges is
too low, and ought to be carefully considered
in this case. The Corrugated Company pro-
posed
width of Roadway of Twenty Feet
and two sidewalks OF five feet each. Col
Albert says that one sidewalk would be ample,
and by emitting one sidewalk and thus reduc-
ing the total width to twenty-five, retaining at
the same time the load of 2.250 per linear
foot OF bridge for the 1877 foot spans there
would result an increase Of working strength
of 20 per cent, or load per square foot of
ninety pounds, which would provide to some
extent at least, for dynamic strains. He there
fore recommends that the width OF the bridge
be
Reduced 10 Twenty-Five Feet.
The company are willing to subscribe TO the
specified width or piers. Col. Albert finds fault
with the construction and height OF the piers
as inadequate 10 stand longitudinal strains,
as proposed by the company, who state
their inability 10 make the desired change In
this respect. While the Corrugated Company
are willing to make the reduction in width,
they offer no increase in the masonry as an
equivalent therefor. Mr.. Albert also says
that before work ON any contract could be com
mpnCel there wOull he rpullifpl additional
ar preparation for the payment OF contingent
expenses of engineering and uperintendence.
In addition to the ordinary engineering and
o11ice expenses there will be required an in
spector OF masonry on each pier in progress
and an expert inspector of bridge and IRON
work TO be present at the works while the Iron
is being rolled and the timbers of the bridge
assembled for the trusses. An Appropriation
of $14,00O for contingencies is recommended,
as the work may extend over year and u
half. Col. Albert submits the following
Conclusions and Recommendation: (:
"In the last letter Of the company, dated Feb
ruary 16, they propose TO build the additional
masonry for the piers for 50,OO0 In addition
TO the contract price. AS their original bid for
the entire masonry was only $36, 600 Tor about
half the actual cost, and as the net cost of
raising the piers to the centre, or point of sup
port of the trusses, is only $4,000, presume
that the amount named by Mr.. Douglass is n
mistake. In any event, his proposition, being
aviolation of act OF appropriation, and also Of
section 1888 of the Revised Statutes, could not
be entertained. The company at first proposed
to build solid masonry piers TO the joint sup.
port or the trusses, and subsequently modified
their original proposal by the substitution of
the cheaper and Inferior construction Of iron
posts. On similar grounds of economy they
might have removed the stone work to a lower
level, and replaced 1t by iron posts.
81 think there can be no question that If these
posts shall be accepted in lieu OF masonry the
bridge would be found after the wear of a few
years deficient in longitudinal stiffness and
stobility. The Introduction OF second series OF
streets as proposed running from the piers to
the panel point, and the introduction OF dag
onal bracing above the arch would strengthen
the construction, but this would involve
further correspondence and delay, which
might be prolonged until II was too late for
the action OF Congress, and thus delay the
work another year.
"The King Bridge Company have already
written several letters complaining that the
Corrugated Metal Company have been al
lowed To modify bids and plans, and have
formally requested that they be allowed TO
modify their bids and plans also and 10 bid
for substructure.
''The King Bridge Company made no bid
originally for substructure, and for that rea-
son their proposal was not considered. As tho
question has been raised, however, l think
there are doubts as 10 the propriety OF allow
Ing bids 10 be modified.
"Upon reviewing the entire subject can see
no reason why the United States should erect
a bridge which shall be inferior in any re-
spect, or one in regard TO which there eau be
any question In the future as 10 durability or
strength. AS already stated,
An Additional Appropriation
for contingencies Will be required in any event
before the work can be commenced, and be-
lieye II would be wise economy at the same
time 10 ask for a sum sufficient To
build substantial and durable bridge"
He submits estimates for such n
| bridge. AS II mas not been practicable
| for want OF funds 10 obtain any precise in
| formation as TO the depth OF the rock, any
| estimate cost OF the bridge must necessarily
| be approximate. Col Albert estimates the cost
| Of bridge with the iron structure below
| grade, with masonry. of a somewhat better
| class Than proposed by the Corrugated Metal
Company, as follows; Masonry, $500; cof-
fer-dam, $4,000; approaches, $1,000; supor-
| structure, S7S,50O; contingencies, $4,000;
total, s2Ol,OOO. Deduct amount appropriated,
| $4,000, leaves a balance of $61,O0O.
| The cost Of a bridge with the same class OF
masonry as now proposed would be S1SS, 800.
| The estimate for a bridge with the iron struc-
turo above grade with pieces sixty feet high
| would be $22O,OOO.
| For the above reasons Col. Albert recon
mends that the proposal OF the Corrugated
| Company be declined; that an additional ap.
| propriatlon be asked, and that section OF the
act of February 23, 1881, authorizing the
| construction OF the bridge, be amended 50 as
| 70 allow the expenditure OF amounts required