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Although the New York State Department of Transportation (NYSDOT) has not yet published guidance on addressing climate change impacts as part of the NEPA process, the organization has been considering the potential impacts of sea level rise on proposed projects during the NEPA process for several years. NYSDOT is concerned about the impacts of climate change, especially sea level rise and riverine flooding, on transportation infrastructure. Sea level rise may flood assets that historically have not flooded or have only experienced infrequent flooding in the past. For example, NYSDOT evaluated potential climate change impacts on the Tappan Zee Bridge reconstruction project.
The Tappan Zee Bridge is a major transportation link and a large financial investment that is designed to have a long useful life. In 2013, NYSDOT performed analyses for the environmental impact statement (EIS) to determine the potential for adverse or beneficial impacts in many categories, including climate change. Specifically, NYSDOT considered the potential for flooding during the 1% annual probability flooding levels on top of end-of century sea level rise. Under this scenario, neither the bridge nor the touchdowns are projected to be exposed to flooding. NYSDOT also looked at the potential for sea level rise to decrease the vertical clearance under the bridge, thus impacting the navigable waterway.
NYSDOT does not have publicly available guidance at this time on addressing the impacts of climate change in environmental reviews.
Since 1955, the existing Tappan Zee Bridge has been a main thoroughfare for residents and commuters between Rockland and Westchester counties. A new crossing is intended to addresses limitations and shortcomings of the existing bridge, including structural, operational, safety, security, and mobility needs.
Concurrent environmental review and procurement processes for the project began in 2011. Figure 1 shows the location of the existing and replacement bridge.
The new bridge is designed to last 100 years without major structural maintenance and will cost $3.9 billion. Figure 2 shows an artist’s rendering of the new bridge. It is being constructed immediately adjacent to the existing bridge and is built for mass transit, with improvements that allow bus rapid transit, light rail or commuter rail. The bridge will also accommodate non-motorized traffic by including a bike and pedestrian path. Construction began in 2013 and the full bridge is expected to open in 2018. Figures 3 and 4 show the new bridge under construction.
The analysis of effects of climate change on the project focused on potential flooding and failure to meet the US Coast Guard air draft limitation requirement (the distance from the bottom of the bridge to mean high water) due to changes in sea level. If the air draft is lessened due to sea level rise, then tall ships may not be able to use the waterway. The steps followed for the analysis include:
The analysis found that the bridge and its approaches are not expected to flood during future 1% annual probability coastal flood levels.
The EIS did not recommend action to address sea level rise since the Tappan Zee Bridge is not vulnerable to current or future flooding.
New York State Department of Environmental Conservation (DEC). Climate Change Guidance Documents: http://www.dec.ny.gov/regulations/56552.html
New York State Sea Level Rise Task Force. Report to the Legislature. December 2010. http://www.dec.ny.gov/docs/administration_pdf/slrtffinalrep.pdf
Tappan Zee Hudson River Crossing Project Website: http://www.newnybridge.com/index.shtml
Tappan Zee Hudson River Crossing Project Environmental Impact Statement Chapter of Energy and Climate Change: http://www.newnybridge.com/documents/feis/vol1/13-energy-and-climate-change.pdf
Tappan Zee Hudson River Crossing Project Environmental Impact Statement Executive Summary: http://www.newnybridge.com/documents/feis/vol1/00-executive-summary.pdf