Walnut Lane Bridge

Walnut Lane Bridge

The Walnut Lane Bridge (NBI #39074) is a Philadelphia historical bridge that was constructed in 1907.  It is a concrete arch bridge that connects the Germantown and Roxborough areas of Northwest Philadelphia.  It was added to the National Registry of Historic Places in 1988 and is #88000815.  This bridge allows people to move across the Wissahickon Creek in Fairmount Park where originally they had to have taken hour long detours around the Wissahickon Creek Valley which was very deep and difficult to maneuver through.  There were a few low level bridges present  It was originally designed as a bridge called the Pont Adolphe which is found in Luxenbourg.  The design was copied and adopted to fit the gap in Philadelphia by the Philadelphia Department of Public Works.  The chief engineer was George S. Webster who was assisted by Henry Quimby.  At the time of its completion, it was the longest and highest concrete arch bridge in the world.  The construction was done in conjunction with the Henry W. Horst Company and Reilly & Riddle contractors.  The project was a direct result of the City Beautiful movement which was a reform philosophy in Northern America during the 1890s and 1900s.  It focused on introducing a sense of class and prestige into the monuments and public buildings/ bridges found in the big cities.  It is currently owned by the State Highway Agency and is managed by the local Town/ Township Highway Agency.  

The construction began on July 5, 1906 and was completed sometime between 1907 and 1908, depending on which source is examined.  The total cost hovered around $260,000 dollars which is about six million dollars present day dollars.  Upwards of 40,000 tons of rubble concrete were used in molding the falsework which was created using steel bents and lumber.  Reinforced steel was not used much due to its scarce nature at the time.  The deck encompassed 3151.26 m2 total and handles a total of 16,810 cars per day, 4% of which being trucks.  Concrete was still a relatively new building material at the time however it was a good fit for the arch bridge as in arch bridges, the dead and live loads are both dissipated into the arch and therefore into the piers due to the curve.  Concrete is not good for bridges that have a great deal of tension but are good for compression.  Arch bridges have a great deal of compression forces pushing on the very sturdy and numerous pillars.  Concrete also satisfied the need for a scenic bridge which was necessary, thanks to the bridge crossing the historic “Forbidden Drive” now known as Wissahickon Drive which was so treasured that automobiles were not allowed to drive on it at the time.  The main bridge is broken up into six main segments.  The first three and last two spans in between the piers are each a 53’0” clearance.  The main arch has a 233’0” clearance with much smaller arches on top of the main arch and passes over the entirety of the Wissahickon Drive, Briddle Path and the Wissahickon Creek.  This fairly long span is very useful to the area and if it were to be closed, drivers would have to travel an extra six miles around another bridge to serve the same function as the bridge.  The most active time period for the bridge was in the 60s and 70s.  The construction of this bridge did not go perfectly.  The “Tragedy at the Walnut Lane Bridge” occurred in December of 1907.  The falsework that was holding poured concrete collapsed and sent around twenty workers flying down the fifteen story fall.  Bernard Mers and James Lawson were both seriously injured and Martin Simpson lost his life.  The bridges history is also filled with many deadly car crashes and suicides, coming to be known by a few locals as the “suicide bridge.”  

Its original design as being the largest concrete arch bridge in the world came to an end soon thereafter when the Rocky River Bridge (Detroit Avenue Bridge) beat it out by about fifty seven feet. It is however one of a fewer amount of unreinforced concrete bridges around.  Because of this, the bridge has started to show some wear and tear.  A 2010 inspection of the bridge found that pieces of concrete were falling from the bridge into the valley and the Forbidden Drive.  A shed was constructed to guard trail goers from the debris after a short closure of the trail.  The most recent database from the National Bridge Inventory rated the deck, the substructure and the superstructure at a 5 on a 0-9 scale.  This is described as being in fair condition which means that “all primary structural elements are sound but may have minor section loss, cracking, spalling or scour.”  A $7.1 million dollar renovation of the bridge was announced in 2011.  It was originally planned for 2013 but had to be pushed back to 2015 and then was rescheduled again for 2016.  In article by philly.com, Emily Babay describes the current plan in which the bridge will be closed for about six months, reopening in October hopefully.  The work is being done by the Buckley and Company Inc. of Philadelphia.