North Carolina Highway 12 Storm Recovery
The North Carolina Department of Transportation (NCDOT) is implementing several different solutions to address frequent overwashes, erosion, and more severe damage to North Carolina Highway 12 (NC 12) following Hurricanes Irene and Sandy. These measures, intended to improve the future resilience of the highway, include bridge construction and temporary beach nourishment.
NC 12 is located along a barrier island between Pamlico Sound and the Atlantic Ocean, providing the only highway linkage through North Carolina’s Outer Banks. Storms frequently cause overwashes along NC 12 that deposit sand on the highway, and shoreline erosion also regularly threatens the roadway. The highway experienced significant damage during Hurricane Irene in August 2011. Due to severe winds and surf, NC 12 was completely severed in two locations: north of Rodanthe (Rodanthe breach) and within the Pea Island National Wildlife Refuge (Pea Island breach). Each of these breaches left behind a 100-foot-wide gap in the barrier island where the highway was disconnected and water freely flowed between Pamlico Sound and the Atlantic.
NCDOT is developing solutions for multiple locations along NC 12 to help increase reliability of the highway in light of frequent storm events and to provide long-term solutions for the areas most vulnerable to erosion. Phase I of this effort, known overall as the Bonner Bridge Replacement Project, involves replacing the existing Bonner Bridge over the Oregon Inlet at the north end of the Pea Island National Wildlife Refuge. The bridge has required frequent maintenance and repair, including scour protection efforts to prevent erosion of the sand around the bridge supports. The new 3.5-mile bridge will allow for natural channel movement and ensure that shoreline movement will not endanger the bridge through at least 2050. A design-build contract for $216 million was awarded in 2011 for the Bonner Bridge replacement, but was delayed until summer 2015 due to litigation. The project was approved to move forward in September 2015; construction began in March 2016 and the new bridge is expected to open to traffic in November 2018.
In Phase II of the project, NCDOT is constructing an interim bridge over the Pea Island breach while the agency continues to study long-term options for reliable travel around the breach, including a possible permanent bridge within Pamlico Sound (i.e. outside of the Pea Island Refuge). NCDOT initially constructed a temporary bridge to restore access over the Pea Island breach, and proposed the construction of a permanent 2.1-mile-long bridge within the Refuge to replace the temporary bridge and adjacent sections of existing surface road. When proposing the permanent bridge, NCDOT considered coastal conditions including potential expansion and migration of the current Pea Island inlet through 2050, based on data collected by NCDOT’s coastal monitoring program in 2011. The coastal monitoring program considers changes related to shoreline location, dune movements, erosion rates, and vegetation. NCDOT is now re-evaluating permanent bridge solutions for bypassing the Pea Island breach. NCDOT agreed as part of a litigation settlement in June 2015 to evaluate bridge alternatives within Pamlico Sound rather than proceeding with plans to construct a bridge on land through the Refuge. While NCDOT conducts studies on alternatives, the agency will construct a new interim bridge for the Pea Island breach area, which will be easier to maintain than the temporary bridge initially constructed. The interim bridge is expected to be completed and open to traffic by April 2017.
Also as part of the second phase of the Bonner Bridge Replacement project, NCDOT completed temporary beach nourishment near Rodanthe and will be constructing a permanent bridge within Pamlico Sound as a long-term solution to travel around the Rodanthe breach. Additional damage to this portion of NC 12 occurred during Hurricane Sandy, most notably at the highway’s “S-Curves,” a region where the shoreline routinely experiences very high wave energy. This winding section of NC-12 has been rerouted several times during the past 50 years as a result of storm damage. During Sandy, water and sand inundated the entire area and buckled the asphalt. Over 3 miles of protective dunes alongside the highway were also lost to severe beach erosion. Without the beach to act as a buffer, subsequent storm events resulted in further damage and closures along NC 12.
In March 2013, Governor Pat McCrory declared a state of emergency for NC 12 in order to help NCDOT move ahead with a short-term solution to protect the vulnerable S-Curves. In response, NCDOT executed an agreement with the U.S. Army Corps of Engineers (Corps) to nourish the beach along the S-Curves. Beach nourishment was chosen because it allows natural processes to create a buffer that can adjust with different storm dynamics. The project, which replaced 1.7 million cubic yards of sand, was designed to provide 3 years of protection for the S-Curves until a long-term solution can be built. The beach nourishment project cost $20.3 million and utilized emergency relief funding authorized by the Federal Highway Administration after Hurricane Sandy. Work began in July 2014 and was completed in September 2014.
NCDOT and other partners on the project team recently approved a preferred design for a long-term bridge around the Rodanthe inlet. The bridge will extend into Pamlico Sound between the southern end of the Pea Island Refuge and Rodanthe. This design alternative will maximize reliable access along NC 12 and avoid the frequent maintenance that is required along the existing roadway and S-curves, in addition to minimizing impacts to the Refuge, natural shoreline, and Rodanthe community. The Rodanthe Long-Term Bridge is estimated to cost between $178 million and $198 million. This part of the project is still undergoing environmental review; public meetings are expected to begin in spring 2016 to publicize this preferred alternative and comments will be solicited, after which a final Selected Alternative will be identified.
NCDOT initially began studying replacement alternatives for the Bonner Bridge in the 1990s. Recognizing increasing threats from erosion and overwash, NCDOT expanded the scope of the study area in 2002 to encompass NC 12 south of the Oregon Inlet to Rodanthe. NCDOT convened a panel of experts from FHWA, the Army Corps of Engineers, US Fish and Wildlife Service, and universities to evaluate long-term solutions (through 2050) to provide transportation across the breach sites caused by Hurricane Irene; this panel issued findings and recommendations in June 2012. The Bonner Bridge Replacement Project was held up between summer of 2011 until summer of 2015 by litigation between NCDOT and the Southern Environmental Law Center, representing conservation groups. The parties reached a settlement in June 2015, allowing construction of the Bonner Bridge replacement over Oregon Inlet to proceed, but requiring NCDOT to cease any plans for a permanent bridge through the Refuge and re-evaluate bridge design options that go through Pamlico Sound instead.
This Adaptation Clearinghouse entry was prepared with support from the Federal Highway Administration. This entry was last updated on March 31, 2016.
- North Carolina Department of Transportation (NCDOT)
- Case study