Big Falls Road over Gunpowder Falls
The Baltimore County (MD) Department of Public Works aimed to replace of one of its aging and deteriorated concrete arch bridges with an economical, safe, low maintenance and aesthetically pleasing structure. The final appearance of the bridge was crucial as it would be located along the boundary of Gunpowder Falls State Park in predominately rural northern Baltimore County. Through preliminary design studies it was determined a precast, prestressed concrete girder stringer/deck slab bridge with a solid parapet would best satisfy all the intended goals of the project.
The new bridge is an 88’ long, AASHTO Type III concrete girder bridge carrying two 11’ lanes, two 3’ shoulders and two Type F shape parapets. The exterior face of the traffic barriers on the bridge and wing walls have an inset, formliner finish that blends the structure into it forested environment. The substructure is composed of two cast in place abutments founded on auger cast piles. The project also included some minor re-alignment of the approach roadways to remove a hazardous horizontal curve in the roadway at the stream crossing.
The County received Federal funding for both the design and construction phases of the project. As part of the Federal funding requirements as well as environmental permitting, the project was subject to the Categorical Exclusion review process and required a Section 4(f) evaluation due to the historic nature of the old bridge. In addition to the environmental evaluation a meeting was held to solicit public input and support for the project.
A low bid of $1.57 million was received in March 2007 and included a item bid of $199,000 for the six main AASHTO Type III girders. The winning bid was roughly 7% below the engineer’s estimate. Work began on the project in September 2007 and was completed in November 2008. Construction operations were virtually problem free and the project was completed ahead of schedule and within budget.
The finished structure fulfils the initial intent of Baltimore County and resulted aesthetically pleasing, low cost bridge that will require minimal maintenance for many decades to come.