Engineers Week: Replacing a Lifeline Bridge in Chemung County
It's National Engineers Week! Engineer’s week highlights the impact engineers have on our world, brings engineering to life for students, and increases public dialog about engineering. So many of us live near water and rely on bridges every day. Read on for insight on some of the challenges engineers solve to keep us high and dry.
State Route 427 Bridge Over the Chemung River
The State Route 427 bridge over the Chemung River is a vital bridge, providing a major river crossing between New York and Pennsylvania that is a critical route during flooding events. In 2013, bridge preventative maintenance revealed that replacement was necessary. The New York State Department of Transportation selected a design-build delivery method, where the builder and engineer work together to design and construct the bridge as a team. LaBella joined forces with Economy Paving Co., an experienced bridge contractor, and Prudent Engineering, who provided construction inspection and construction quality control.
The team's task was complex: the bridge would need to be constructed and ready for traffic in one construction season, and below it, the Chemung River is prone to rapid fluctuation in volume and depth. Additional construction challenges were identified by the presence of endangered and threatened freshwater mussels in the river. The Chemung River is categorized as a Class A regulated stream, which means that it is a source of water supply for drinking, and a primary and secondary contact for recreation and fishing. The construction plan relied heavily on work done by the NYS Department of Environmental Conservation (DEC) and the DOT for environmental permits and the relocation of endangered mussels.
In every project, minimizing impact to the environment and public is paramount. To achieve this project's goals, the design team employed a number of strategies. First, the design was tailored to suit the strengths of Economy Paving. The superstructure was designed into segments sized for Economy's cranes. The structural design opted for two identical bridge structures in series, rather than a 800' long single bridge. The pair of structures simplified design and detailing, and reduced cost.
Second, the new bridge was constructed near parallel to the existing bridge. Not only did this allow for two way traffic for the vast majority of the construction process, the existing bridge served as a construction platform for concrete placements and steel reinforcing on the new bridge.
Third, the design included features to facilitate future maintenance and rehabilitation, with the intention to avoid future impact. Since this bridge has been identified as a vital part of the local infrastructure, a complete bridge closure to perform a future deck replacement is not possible. This is why the team elected to design and construct the new bridge deck as a traditionally reinforced concrete slab. This will make a future deck replacement possible while utilizing staged construction with one-way alternating traffic.
One of the things that makes this project stand out was the teamwork we developed with Economy Paving. When design-build partnerships are effective, the resulting project is innovative and expedient.
The river was a major player in this project. Throughout the course of construction, its depth varied from as low as 2 feet, to as high as 8 feet. A gauging station provided real time updates, and work was performed when low depths made it advantageous to do so. We worked closely with regulatory agencies to develop the construction schedule around when we could safely be in the water without impacting the river as a habitat.
As a structural engineer with a specialty in bridges, it's exciting and encouraging to see renewed investment in our bridge infrastructure. My father was a structural engineer and steel fabricator, and he raised four engineers (and three doctors). My siblings are chemical/nuclear, bio-chemical/pharmaceutical and aerospace engineers. Celebrating engineers and Engineers Week encompasses so many things. What you learn in school just scratches the surface. The important thing is to keep learning, following your interests, and your specialty will choose you.