Southeast SD emergency managers on alert for overwhelmed sewer systems, high river levels

Regional authorities have their eyes on sewer and river systems as intense rainfall continues to wash over Sioux Falls and parts of southeastern South Dakota.

Heavy rains have inundated the region to the point where daily rainfall records were broken Thursday in Sioux Falls, Mitchell and Huron, with precipitation persisting into Friday.

The influx of rainwater has the region's emergency managers and authorities closely monitoring sewer intake and how that might affect stream and river levels.

In Sioux Falls, City Emergency Manager Regan Smith told the Argus Leader on Friday the city's 26-mile levee system, which limits flooding along the river's channels and Skunk Creek tributary, is "performing well."

But river levels are a concern worth monitoring, Smith explained. Gage measurements at some points along the Big Sioux River have seen a "significant rise," the emergency manager said, reflecting the rain's strain on the city's sewer system.

"Our water reclamation plant is experiencing high inflows of sanitary sewer [water], so we're watching that," Smith added.

The city of Lennox, meanwhile, has been under greater strain. City Administrator Nathan Vander Plaats declared the town was in an "emergency flood situation" late Thursday night.

Vander Plaats told the Argus Leader he's heard multiple reports of home basements being flooded and roadways becoming impassable due to the rain, though the town's main thoroughfares have been drivable since noon.

However, the city's sewer system has been unable to keep up with the large amounts of rainfall, the city administrator said, leading water to back up into a few homes in a specific part of the town.

With the National Weather Service predicting more rains, with some storms severe, to hit southeastern South Dakota by 5 p.m. Friday, Vander Plaats said it's becoming a race against the clock to push out as much flood waters before then.

"We're actively fighting it at this point," Vander Plaats said. "We're pumping out everything we possibly can to make more room for tonight."

The threat of high river levels also played out Friday near the town of Brandon, after emergency crews were dispatched at about 9 a.m. Friday to Huset's Speedway to rescue stranded campers parked near the race track.

An Argus Leader reporter observed at least 8 RVs stuck in knee-high flood waters, which likely stemmed from Split Rock Creek, a waterway close to the speedway's parking lots. Rescue crews were seen deploying inflatable boats to transport trapped campers out of the flooded area. At least two people were taken by boat to higher ground.

According to U.S. Geological Survey data, gage measurements north of Brandon, though not necessarily reflective of exact stream depths, rose from 3.85 feet on Thursday to more than 12 feet by 7 a.m. Friday.

Minnehaha County's roads as a whole have been weathered in parts by the flooding, per county EMS Director Jason Gearman. He told the Argus Leader "lots of roads" were under water Friday morning, which has led the county to set up barricades at the most flooded sections of street.

At least one water rescue was carried out Friday morning near Brandon as a result of a driver maneuvering around a barricade, Gearman said.

This article originally appeared on Sioux Falls Argus Leader: Flooding in South Dakota puts emergency managers in race against clock