Wednesday's rain deluge in Minot left many streets with pooling water and made certain roadways impassable.
Minot public works director Dan Jonasson said the rainfall was a 150- to 500-year event, while the city's storm sewer system largely is designed to handle an event that might occur every 25 to 50 years. The system is designed to take an average of half an inch to three-quarters of an inch of rain an hour.
Jonasson said reports of 3.25 to 5 inches of rain in spot areas of the city came too quickly for the sewer system to handle.
"It was just that exceptional," he said of the storm that had water filling up streets that typically stay well drained.
"The storm drains aren't designed for anything like that. To design a pipe to take that amount of rain in that amount of time would be millions and millions and millions of dollars," he said. "You never design to that. You design to more of a 25- or 50- or 100-year storm standard."
The 16th Street Southwest and Burdick Expressway intersection often is one of the first intersections to take on water. Jonasson said as a part of the hazard mitigation project to bring flood protection to the water treatment plant area, the storm sewer system will be analyzed. However, he added, the analysis is only to look at improvements to ensure the system can handle a 25- to 50-year event.