Evening star. [volume] (Washington, D.C.) 1854-1972, 1905-01-11

cased in a concrete platform. the whole
construction having a depth of about four
feet, are contemplated, while in South
Washington the bridges will be the more
usual construction of plate gtrders with
solid trough floors to carry the ballast.
1.-THE bridge carrying New York avenue
over the terminal tracks just beyond the
city limits has been designed on special
lines. y 1t was the wish to use masonry
structure. but the skew was such that this
was not practicable and the construction
was designed Of Orders encased In con-
crete supported by steel posts. similarly en-
cased. Stimulating a masonry construction.
Although this construction Is only planned.
yet confidence Is felt that the treatment Is
fully adequate.
"A feature of the terminal structure is the
length of the street subways, where Fl
street. X street and l. street northeast. are
carried below the tracks. In the case Of H
street this length Is about 500 feet: in the
case Of K street, 400 feet, and OF l. street.
200 feet; the first named case being the
longest similar subway of which / have
knowledge. In designing these subways
some special types Of construction were
used. Provision has been made for their IL
Illumination during the daylight hours In
part by openings through the roof Of the
subway, and in part by the introduction of
special skylight construction into the rail-
road platforms, which form part Of their
roof. These skylights consists Of bulls-e
lenses of glass imbedded in reinforced con-
crete, the glass constituting some 30 per
cent of the total area Of the skylight 1t
is designed to prevent condensation on the
walls of H street subway by the use of
special facing wall of brick separated by
an air space from the main wall, the inter-
vening air space being designed to prevent
the constantly relatively low temperature
of the ground behind the main wall from
communicating to the face of the wall, and
thus producing condensation. Owing to the
opinion of the railroad engineers that this
condensation would not drain, and there
being some feeling of doubt in the District
engineers office as to the absolute neces-
sity of this construction. the founda ions
only have been built The construction of
the facing wall itself will be postponed I'M
til it's desirability Is developed. as a result
of actual experience with the subway when
completed.
Waterproofing the Work.
"Throughout the entire work the most
careful consideration has been given to
the matter of waterprooflng the overhead
bridges and the sidewalks. The practice
of other communities in this particular has
not been the sole guide in this matter
but advanced types Of construction, 1t Is
believed, have been developed, it being
planned to make very general use of an
oxidzed Texas Oil from which the hydro
gen has been drawn, known to the trade
as Hydroline B. This is very tough
elastic substance which gives promise of
being very effective waterproofing ma
terial.
'The general practice in designing street
subways in other cities has been to place
posts at the curb line and carry the tracks
across the roadway by a single span
departure from this has been made i'll the
Washington work, posts being so located in
the roadway to give a center span of
twenty-five feet for present or future
street railway use, fianked by spans of ap-
proximately equal length. The roadway
width is thus free for adjustment traffic
conditions change, while the bridge struct-
ure is stiffened and cheapened.
The changes of grade of the streets and
the closing of other streets within the site
Of the terminal structure have necesstated
extensive reconstruction of subsurface ap
purtenances, the relaying of water mains
and the reconstruction of sewers. A single
case of this kind was the diversion, at a
cost Of S45, 900, of the nne-and-a half foot
sewer, which crossed the site of the union
station, while at Florida avenue where it
crosses the terminal structure extensive
reinforcement of the sides of the sixteen
foot sewer in that street, using concrete
reinforced with steel beams, was resorted
to as a precaution against displacement by
the abutments Of the railroad bridge. the
sewer in this case being within eighteen
inches Of the new street grade.
LAS far as such things may be the
aesthetic qualities have been sought in de-
signing the structure in view from the
streets, and consideration has been also
given 10 proper provision Dy pdrapet walls
and screen fences against disturbances of
the street traffic by the operation of trains
on the viaducts.
State Of the Work
''At this date the state of the work is
briefly as follows: The new Long bridge is
completed and in use, and the highway
bridge adjacent thereto is nearing compile
ton. The Virginia avenue tunnel-half a
mile long-is nearly finished. This tunnel
is a single tube for two tracks. The work
in South Washington between South Capitol
street and the Long bridge has been pur-
posely postponed until after the Inaugural
ton. The LIST street tunnel-4 500 feet long
in all-is practically completed for about
LOCO feet at Its south end and 500 feet at
its north end. This Is twin tunnel for
two tracks, one in each tube. Almost all
the uncompleted portion will be constructed
by tunnelling, the completed portion hav-
ing been made by cut and cover. The foun-
dations of the union passenger station are
about one-thrd completed; work on the
station building itself has not yet begun.
THE other terminal structures and via
duct in the northeast section are about
three-Quarte1s completed, and the same pro-
portion of work has been done on the grad
ing of the terminal yards ETC., beyond
Florida avenue. The Pennsylvania railroad
northern connection to Magruder station Is
nearly completed. 1t is hoped that the ter
mlnais Will be in use, though not entirely
So-'tPiNeSu' AZ aoouI iWo years from now.
There have been no engineering features
OF dlfhculty, the interest of the work being
In Its size and the important results obtain
ed. The foundations are usually good. on a
clay bottom. In the case of part of the
side wall foundation of K street north
the upper crust of the clay bed was cut
through and the soft blue clay bed below
was SO unsuitable that piles were driven. In
driving the list street tunnel from the south
end 1t was feared that the foundation would
not support the shield and superying
weight, and it was proposed by the CON
tractor to use an open cut. This plan was
abandoned. however, and the work is now
being done with shield without diff
culty. A gravity concrete mixer has been
used with apparent success in a large part
of the work.
CHINA NOTIFIED.