View south (downstream right), Maple St intersects from right beyond bridge
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Allegheny County Bridge Number 5 McLaughlin Run
McLaughlin Run Rd #5 over McLaughlin Run
USGS 7.5" Topo Quad - UTM Coordinates:
Bridgeville - Zone 17; 0575-4467
McLaughlin Run Rd [S.R.3004, Orange Belt]
-- at Maple St
-- McLaughlin Run
TYPE OF CONSTRUCTION / DESIGN:
riveted steel plate girder
abutments: locally-quarried sandstone, rock-faced coursed ashlar
LENGTH OF MAIN SPAN:
TOTAL LENGTH (including longest elevated ramp):
HEIGHT OF DECK:
YEAR ERECTED / ENGINEER:
1905, Allegheny County
Charles Davis, engineer
A metal builder's plaque is riveted to the center of the downstream girder:
- - - -
- - - -
KING BRIDGE CO.
During years surrounding 1900, Allegheny County, under the direction of County Engineer Charles Davis, was busy throughout the county building stone arch bridges of a simple and similar design. In some places, however, the crossings were built as riveted plate girder spans. The abutments of these girder bridges exhibit similar stonework to the County's stone bridges -- helping to identify their place in time and origin. A glance at the construction dates indicates that many of the earlier bridge were of the girder type.
One possible explanation for the choice of an arch span versus a girder span may be found in the shape of the land onsite. Where the stream has high banks and can therefore hold rising waters of a flash flood, the bridges are usually stone arches. In places with relatively wide, flat channels, the spans are most often girders. In each instance, the goal was to maintain the level of the road surface as the road approaches and then enters the bridge -- while allowing maximum potential stream flow; sites which made this impractical have since been regraded or replaced.
Allegheny County assigns its bridges with an ID number counting from a stream's outflow, sequentially upstream. This was the fifth bridge upstream from the point where McLaughlin Run flows into Chartiers Creek.
On the inside of the downstream girder, there is a hand-drawn diagram with notes regarding the deck structure. In its 15 inches of thickness, there is a 7 inch thick metal grid base, topped with 2 inch thick brick, covered with a 6 inch thick layer of asphalt.
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