This was once a part of the Atglen & Susquehanna Branch, a Pennsylvania RR low-grade freight bypass of Lancaster between Columbia and Atglen, and used to carry several freight trains a day between the Harrisburg area and points east; Conrail acquired PRR successor Penn Central in 1976 and later shifted through freight trains off the ex-PRR Harrisburg-Philadelphia-Trenton routes in favor of former Reading RR routes. Conrail abandoned this bridge, and the entire Atglen & Susquehanna, around 1988. Currently it is a part of the planned Enola Low Grade Trail which extends from just outside Harrisburg to Paradise, Pa.
Description and History
In 1902, the Pennsylvania Railroad (PRR) made plans to build a new low-grade freight line across Lancaster County, a decision motivated by steep grades on its four-track main line between Philadelphia and Harrisburg. Called the Atglen & Susquehanna Branch (A&S), or simply the Low Grade, it diverged from the main line at Parkesburg and passed south of Lancaster, through Quarryville and Martic Forge, to Shenks Ferry on the Susquehanna River.
The A&S then paralleled the existing Columbia & Port Deposit Branch (C&PD) of the Philadelphia, Baltimore & Washington Railroad (a PRR subsidiary) along the river's east bank. At Shock's Mills it crossed the Susquehanna on a new stone arch bridge and proceeded along the west bank to rejoin the main line at Marysville. Construction of the line, which consumed "over three and a half years, $19.5 million, and reportedly more than 200 lives," is a story in itself, amply covered by historian Frederic H. Abendschein.
The A&S was but one of a number of improvements to freight operations in eastern Pennsylvania during me admmistration of PRR President Alexander J. Cassatt. Other items proposed by Cassatt in 1902 included grade reduction on the Trenton Cut-Off and construction of the Philadelphia & Thomdale Branch, the completion of which provided a continuous freight bypass around Philadelphia. The 1902 plan let a gap of about ten miles from Thomdale to Parkesburg, between which freight trains shared the main line with passenger traffic. Although the gap was never closed, the Philadelphia bypass and the A&S together constitute initial segments of "a low grade route stretching from the eastern seaboard to the midwest," a vision which Abendschem attributed to former PRR President J. Edgar Thomson, who served from 1852 to 1874.
Construction on the A&S began with the Shock's Mills Bridge in late 1902. As work proceeded, a 1904 flood turned over the six-span stone arch bridge that carried the C&PD tracks over the Conestoga River. Rather than rebuild this bridge, PRR evidently decided to incorporate its replacement into a new bridge for the A&S. As the two lines travel south from Columbia, the C&PD descends to follow the river while the A&S ascends in preparation for its turn to the east. (Where the lines diverge at Shenk's Ferry, these two lines are 150'-0" apart in elevation.) The new Conestoga River bridge was therefore designed with two levels, with the C&PD's two tracks at 55'-0" above the 1905 river level, and A&S's two tracks 92'-0" higher and 96-0 to the east. The C&PD spans, riveted deck plate girders 98'-6", 98-0", and 98'-6 long, comprise the entire 295'-0" length of the lower level. At the upper level, the A&S spans include not only a 300'-0" pin-connected Pratt deck truss over the river, but also plate-girder viaducts on steel trestle bents, nine spans totaling 480'-0" on the north approach, and seventeen spans totaling 780'-0" on the north. The high stone piers supporting the 300-0 truss are monolithic with the lower level abutments.
PRR's wholly-owned subsidiary, Pennsylvania Steel Co. of Steelton, fabricated all of the steel work, which was erected by the contractor on this section, H. S. Kerbaugh, Inc., during 1905. Construction photographs show that the high stone piers and falsework for the 300'-0" truss were built concurrently. During this time, the C&PD used a temporary wooden trestle off to one side. Erection first began on the 300'-0" truss, aided by a traveler. Shortly thereafter, additional traveling cranes were employed for the north and south approach viaducts, working from the abutments toward the river. Almost all of the high-level erection had been completed before crews began work on the low-level girders. The A&S opened to traffic in July 1906, and the C&PD, which had suffered numerous diversions and interruptions during construction, returned to regular service that August.
Construction of the Safe Harbor Dam in the 1930s raised the river's level considerably, prompting PRR to raise the C&PD grade. Maintenance records indicate that Belmont Iron Works raised the tower spans 4'-0" and installed reinforced concrete bridge seats. While the former G&PD continues to see freight traffic, then-owner Conrail removed tracks from the upper level in 1990, after abandoning this portion of the former A&S.