DOT says unusual rain led to unusual flood
Published 12:00 am Wednesday, December 2, 2009
By Mark Wineka
The East Innes Street area near Interstate 85 is not your typical flood plain.
Commercial and highway development has made it one large impervious surface. Combine that runoff with Town Creek and an unusual amount of rain, and you find yourself in deep water.
David Black, resident engineer for the N.C. Department of Transportation, said the East Innes Street area near I-85, which was totally rebuilt in recent years as part of the interstate widening project, was designed for 50-year storm standards.
That means, the kind of rain Salisbury experienced is supposed to happen about once every 50 years. Otherwise, the road should handle most storms.
“You get 7 inches of rain with the ground already saturated, and the runoff is phenomenal,” Black said.
“This type of storm (with flooding) has happened before, but it’s been a long time.”
The interchange’s redesign included the installation of a much bigger culvert, with much more water-carrying capacity.
All the drainage in that interchange area was substantially improved, Black said. He didn’t know of anything else that could be done to improve the drainage other than raising the elevation 8 to 10 feet.
Black said the elaborate drainage infrastructure in the area includes two 66-inch-wide pipes tied into a 96-inch wide tunnel under the interstate. The system seemed to handle the drainage on the east side of the interstate, but the downtown Salisbury side ó thanks partly to its being so low ó was overwhelmed.
Steve Weatherford, head of the city’s street division, said the flooding in several Salisbury locations wasn’t because the catch basins were blocked. Rather, when the creeks are full, there’s no place for the water flowing into the catch basins to go, Weatherford said.
Weatherford said Salisbury Police, Salisbury Fire, his street crews and state Department of Transportation workers were responding to the East Innes Street flooding.