The Safe Harbor Bridge (also Safe Harbor Trestle ) is a railway bridge over the Conestoga River , shortly before its confluence with the Susquehanna River . The structure, which was built by the Pennsylvania Railroad (PRR) until 1906 , ran two tracks at different heights. The abutments of the lower girder bridge are also the bridge piers of the main opening of the upper Trestle Bridge , the 91-meter truss girders spanning the entire lower bridge. The upper track level was part of a 115 kilometer long freight route with a slight gradient between the Enola Yard near Harrisburg and the southeastern city of Parkesburg , where there was a connection to the main PRR line to Philadelphia or via the Trenton Cutoff to New York City . The Enola Low Grade Freight Line , which was used until 1988, has been expanded as a hiking trail since the beginning of the 2010s. The lower level led two tracks of the Philadelphia, Baltimore and Washington Railroad , a subsidiary of the PRR. These are now operated by the Norfolk Southern Railway , which took over large parts of the former PRR routes in 1999.
With the increase in rail traffic in the USA at the end of the 19th century, the Pennsylvania Railroad invested heavily in modernizing and expanding its route network. On the main line between Pittsburgh , Philadelphia and New York City in particular , there was increased freight traffic congestion, which led to congestion on the lines and marshalling yards. The extensive construction work included the Rockville Bridge above Harrisburg, a new four-track bridge over the Susquehanna, which was completed in 1902. To the south of this, the PRR built a new marshalling yard on the west bank of the river with the Enola Yard by 1906 and laid a 115-kilometer double-track line for freight traffic southwards to Parkesburg , where it joined the largely parallel Philadelphia – Harrisburg railway line .
The freight route ran from the eponymous Enola Yard to Parkesburg largely along the banks of the Susquehanna, the Trenton Cutoff ran from Glenloch to the bridge to Trenton
Since the east of Pennsylvania is crossed by the Ridge and Valley zone of the Appalachians , the main line here had gradients of about 10 ‰, which meant that the trains had to be split up and equipped with additional push locomotives. The new Enola Low Grade Freight Line (also Atglen and Susquehanna Branch ) was specially laid with a low gradient, at 3–6 ‰ it was significantly below that of the main line. From Enola Yard it ran south along the west bank of the Susquehanna and changed banks about 40 kilometers downstream over the Shock Mills Bridge, completed in 1905 . From there the route followed the east bank of the river via Columbia to the mouth of the Conestoga, which it crossed at a height of almost 30 meters over the new Safe Harbor Bridge .
Since the tracks of the Philadelphia, Baltimore and Washington Railroad (PB&W), a subsidiary of the PRR, ran here and the bridge was damaged in a flood in 1904, the PRR decided on a combined new construction, whereby the bridge piers of the main opening of the upper Trestle Bridge were integrated into the abutments of the lower girder bridge; the bridge was opened to traffic in the summer of 1906. Not far from Safe Harbor, the route then turned east from the course of the Susquehanna and ran east to Parkesburg. A bypass from Philadelphia for trains in the direction of New York City was realized by the PRR in 1892 from Glenloch via Norristown to Trenton in New Jersey ; the Trenton Cutoff crossed the Delaware River from 1903 over the also newly built Morrisville – Trenton Railroad Bridge .
On the right the disused Trestle Bridge , in front of it the lower platform level and on the left the power station of the Safe Harbor Dam (view to the northwest, HAER from 1999)
By 1931, the Safe Harbor Dam was built on Susquehanna about 300 meters from the mouth of the Conestoga . Since the barrage increased the river level in the upper water (Lake Clarke) considerably, the section of the PB&W running here had to be increased, which also caused the lower Safe Harbor Bridge behind the barrage to be raised by 1.2 meters. With the availability of cheap electrical energy from the run-of-river power plant , the PRR electrified the freight route by the end of the 1930s.
Closure of the upper track level
Until the end of the Second World War , the line was highly profitable, but with the expansion of the road network and the emergence of motorized individual transport, the railroad carried fewer and fewer goods and people, which made the large railroad networks in North America increasingly unprofitable from the 1960s and in the following years led to several bankruptcies of the railway companies. In 1970, Penn Central , the successor company of the PRR, was insolvent and in 1976, along with other railway companies, it became the property of the state rescue company Conrail . In the course of the consolidation in freight traffic, Conrail downgraded the routes west of the Susquehanna in favor of the connections running east via Harrisburg. The last train ran over the Upper Trestle Bridge in 1988 and Conrail removed the tracks on the Enola Low Grade Freight Line in 1990 . After the split of Conrail in 1999, the Norfolk Southern Railway (NS) took over the Safe Harbor Bridge with most of the former PRR lines. The lower track level is still operated by NS, while NS sold the upper trestle bridge and the freight route to the corresponding townships in 2008 . Since the beginning of the 2010s, the route has been expanded as a hiking trail in many places (Enola Low Grade Rail Trail) . After securing the financing for the expansion of the Trestle Bridge in 2018, work here is to begin in 2020 and be completed in 2022.
description
View from the lower bridge to the east (HAER from 1999)
The lower track level crosses the Conestoga in an east-west orientation over a 90 m long girder bridge made of three 30-meter solid wall girders that rest on two walled river pillars and the respective abutments . These abutments rise on the north side to the bridge piers for the track level about 11 m above and support a 91 m long parallel - belted truss with overhead tracks. This is designed as a frame framework, whereby the struts and lower chords , which are only subjected to tension, consist exclusively of eye rods . Trestle bridges 146 m long to the west and 238 m to the east are connected to the truss , the latter describing a slight curve to the south. In addition to the central lattice girder, the scaffolding pillar viaduct is divided into a total of 26 solid wall girders supported by 12 steel lattice masts. The total length of the upper track level between the abutments is 475 m.
literature
The Low Grade Freight Cut-Off of the Pennsylvania RR In: Engineering Record. Vol. 52, Part I. No. 25, 1905, pp. 674-677, Part II. No. 26, 1905, pp. 707-710.
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to Parkesburg 
to the bridge to Trenton 
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