Tuesday, December 27, 2016

Edmondson Avenue bridge replacement

The cancellation of the Red Line didn't just affect transit, the loss goes deep into any number of projects the City has on the books. One example is the Edmondson Avenue bridge in West Baltimore. The bridge, constructed between 1907-1912 (pictures of the half finished bridge date to 1909) by the City of Baltimore Department of Public Works carries Edmondson Avenue over the Gwynns Falls valley and the CSX railroad (formerly the Western Maryland Railway).
1909 image of the half constructed bridge (Municipal Journal & Engineer 1909)

The Bridge consists of a four-span, closed spandrel structure constructed of reinforced concrete and extending 541 feet in length and is 87.9 feet wide outside to outside. The structural condition of the bridge  was declared Basically intolerable requiring high priority of corrective action in 2014. The bridge was begun in 1907 as a replacement of an older bridge and was constructed with streetcar tracks  and in two halfs for east and westbound traffic, similar to the approach for its current replacement, leaving the old structure in place to maintain traffic according to the Municipal Journal and Engineer Journal of 1907. The bridhe received a comprehensive overhaul in 1970.
DOT image showing new bridge elevation

The  110 year old
bridge was already slated for replacement when the Red Line was planned to be placed in the median and the design was adjusted accordingly. The modified bridge became one of Baltimore's "in-kind" local contributions to the Red Line project. First bid and awarded in 2015. According to the acting Director of DOT, Frank Murphy, the bridge was put out for bid again this year and awarded for a construction cost of $40 million. According to City DOT the bridge will be fully replaced but look very similar after completion. In 1996 an application was made to place the similar West Baltimore Street bridge (it has open spandrels) on the Federal Register of Historic Places but apparently this bridge  was never designated.

The design of the bridge falls into a period when infrastructure was expected to "conform with the environment" but also use new technologies such as concrete. In a book titled  "Artistic Bridge Design" (1912), bridge engineer Henry G. Tyrrell asserted that bridges are considered beautiful when they

Postcard showing the bridge from the south side from the road that
is today the Gwynns Falls trail (Kildruff)
  • Conform with the environment 
  • Have an economic use of material - "Beauty exists in the structure with the greatest simplicity, fewest members and most pleasing outline."
  • Exhibit  purpose and construction -- "Strength and boldness should predominate."
  • Have pleasing outlines and proportions - "Arches must be perfect curves."
  • Use appropriate but limited ornament -- "Superfluous decoration has a minifying effect.
  • Have an "uneven number of spans is always preferable, for the eye is better satisfied with an opening rather than a pier at the center" 
  • "bridges with several spans should have the longest at the center and adjoining ones should decrease in length towards the end. 
The Edmondson Avenue Bridge complies with this character: reinforced cast concrete construction, uneven number of spans, geometric perfect arches, rectangular pier columns with simple geometric ornamentation, unlike the Baltimore Street bridge, though, it doesn't have open spandrel arches (they were covered with a concrete sidewall), solid parapet construction with minimal recessed detailing and simple cast iron lights a and placement of an urban bridge in a park setting. The concrete surfaces were "bush-hammered with pneumatic tools...by this method the glossy surface of the concrete was removed..and the surface is given a compact granite-like appearance". (Municipal Journal).

Bus and car drivers know the bridge at the low point between Rosemont and Edmondson Village in a much more prosaic way: As a place of standing water after each major rain event that each winter turns into a field of horrific potholes. Pedestrians know it as a treacherous place with minimal 5' sidewalks where people are jammed between the curb and the concrete parapet and helplessly exposed to the splatter of the standing water or the slush in winter. One can hope that the new design allows a few more feet of walk space, even though the space for future tracks should certainly be maintained, just in case Baltimore still gets the Red Line one day.

The bridge looking east with the redirected lanes indicating that the south
half will be done first (Photo Philipsen)
Construction preparation for the bridge has finally started. The concrete median has been removed and paved allowing DOT to move two lanes of traffic in each direction essentially on only one half of the bridge while the other half will be replaced. A similar approach had been taken by the State Highway Administration on the same route a few miles further west where US 40 crosses the Patapsco and a similar but higher concrete arch bridge was recently reconstructed.

The Edmondson Avenue bridge is just one example of the crumbling Baltimore infrastructure. If redone correctly, it will last another 110 years. The bridge carries between 35,000 to 50,000 vehicles a day, many of the trucks and buses.

Klaus Philipsen, FAIA