Twice in the last three years, flooding caused by hurricanes has shut down Eastern North Carolina’s major interstate highways, I-40 and I-95, for days at a time, hampering relief efforts and the flow of people and commerce up and down the East Coast.
Now the N.C. Department of Transportation has developed a set of strategies that might keep those roads open after future storms, at a potential cost of hundreds of millions of dollars.
The strategies generally involve lengthening bridges, improving drainage and elevating the highways in areas prone to flooding. They’re presented as a set of options that in the case of I-40 could involve making alternative routes such as U.S. 421 and U.S. 117 less vulnerable to floods in conjunction with changes to the interstate.
Secretary of Transportation Jim Trogdon commissioned the I-95/I-40 Flood Resilience Feasibility Study after Hurricane Florence dropped record amounts of rain on Eastern North Carolina last year, just two years after Hurricane Matthew. Both storms rivaled Hurricane Floyd in 1999, which caused historic flooding that people never expected to see again.
Citing the Fourth National Climate Assessment, released by the Trump administration last fall, the NCDOT report notes that scientists have measured an increase in rainfall from severe storms over the last century and predict climate change will make hurricanes both more common and intense, “meaning storms like Hurricane Matthew and Florence may become more frequent.”
Both storms closed I-95 and I-40 for a week or more. For several days after Florence, all roads leading into Wilmington, including I-40, were closed because of flooding, prompting the state to consider bringing in supplies by ship.
The NCDOT study was done by the Durham office of Wood Environment & Infrastructure Solutions and looked at options for improving both the interstate highways and alternate routes. But in the case of I-95, the study concluded there were no viable alternatives, because the parallel roads are equally or more likely to flood.
Instead, the study identifies ways that four sections of I-95 in southeastern North Carolina could be made less prone to flooding. It estimates that longer bridges, better drainage and elevating the highway would cost nearly $320 million if done on their own. But in conjunction with other road projects, such as the planned widening of I-95 in the coming years, the cost would come down to $127.5 million.
The study lays out seven options for improving I-40 or alternate routes. Making I-40 itself less prone to flooding, mostly by elevating the roadway or building new earthen embankments in several places, would cost an estimated $169.5 million.
Two options that entail making some changes to I-40 along with improvements to parallel U.S. 117 would be cheaper, at about $51.5 million each. Other options, such as improving N.C. 24 and U.S. 17 or widening U.S. 701 and U.S. 421, would cost significantly more than reducing the risk of flooding on I-40.
Finally, the study also identifies options for improving N.C. 24 between I-95 near Fayetteville and I-40 near Warsaw.
That road is a four-lane divided highway for most of that route, and improvements there could help it serve as a key connector between the two interstates during floods, the report says. The options range from elevating the highway and building a new bridge at Six Runs Creek east of Clinton for $62.6 million to turning the road into a limited-access freeway for $1.2 billion.
The NCDOT report is dated Aug. 28, but spokesman Steve Abbott says it will be updated as time goes on and referred to as the department plans road projects in the future. For now, NCDOT has delayed hundreds of construction projects across the state because of financial problems caused in part by the cleanup and repairs after Matthew and Florence.