PROVIDENCE — Although the storm that dumped between 5 and 7 inches of rain in 90 minutes in the state’s capital on Sunday is being described as “rare,” such extreme weather events are becoming more common — and they’re testing the state’s aging infrastructure.

The heavy rainfall resulted in a two-hour closure of I-95 near the Thurber’s Avenue exit on Labor Day weekend, overwhelming catch basins designed to handle less than 2 inches of rain per hour, making the road impassable and stranding cars already on the highway.

According to a statement from the Rhode Island Department of Transportation (RIDOT), which maintains the highway, Sunday’s “rare storm… severely taxed our stormwater drainage system.” 

But such storms are no longer as rare as they used to be, as RIDOT acknowledged.

“We realize that this type of situation will become more common as climate change accelerates… We are evaluating the capacity of all our systems and upgrading as quickly as possible,” RIDOT said in a statement. The agency has invested $20 million a year in its stormwater management system since RhodeWorks became law in 2016.

“We experienced flooding because the capacity of our system was exceeded by the intensity of the rainfall,” RIDOT said. The agency’s catch basins are designed to handle a 10-year rain event.

“That’s terrible” is how University of Rhode Island professor Kang-Won Wayne Lee described  the system’s capacity. Lee is the director of the Rhode Island Transportation Research Center, which aims to find ways to make roadway infrastructure better and safer.

Lee said that the state should be upgrading to a 25- or 50-year rain event system, meaning that stormwater infrastructure should be able to withstand more extreme weather patterns that aren’t likely to happen frequently, but produce more precipitation when they do. 

More catch basins and larger drainpipes could help increase the capacity of the system, according to Lee. Maintaining the systems that are already in place is also important because debris can cause blockages and flooding even before rainfall becomes too intense, he added.

RIDOT said that pre-storm blockages were not an issue on Sunday. Before the storm hit, RIDOT workers inspected the drainage system and found that it wasn’t blocked around I-95. 

During the storm, RIDOT also sent a crew to the flooded area to keep the system clear of debris. The workers stayed overnight and into the morning.

The 40-inch outflow pipe operated at “full capacity and beyond capacity,” the statement said, noting that the system was designed 50 years ago and hasn’t been upgraded since.

Although Lee recommends the upgrades, he said it’s important to remember that what used to be a once in a quarter- or half-century storm is now much more commonplace — I-95 has already flooded twice this year. 

Colleen Cronin is a Report for America corps member who writes about environmental issues in rural Rhode Island for ecoRI News.