Heavy rainfall across northwest and north central Iowa has overwhelmed some drinking water, sewer treatment plants and animal feeding operations from Lyon to Linn County.
A reported 3 to 5 inches of rain fell Monday night, adding to rainfall over the weekend, with the heaviest rainfall in the far northwest. Heavy runoff is affecting some drinking water systems and making it difficult for many wastewater treatment systems to keep up with the inflow from rainfall.
The drinking water plant in Rock Rapids, Lyon County, has shut down after the clear well was inundated with water. Lyon and Sioux Rural Water have had stream crossings wash out and are rerouting water to try to maintain pressure. Rock Rapids and the Rock Rapids subsystem of Lyon and Sioux Rural Water have issued boil warnings as the rural water system buys part of its water from Rock Rapids. The Rock River near Rock Rapids was 26 feet high at noon Tuesday, up from less than 10 feet on June 14. The flood stage is 13 feet.
In Rock Valley, Sioux County, the city lost power to three of the four wells, but was still operating on the one remaining well.
Flooding on the Big Sioux and Rock rivers is expected to reach historically high levels. People should avoid recreation in flooded streams and rivers.
In Wahpeton, Dickinson County, the water plant has lost power, but the city is buying water from Milford, enabling the system to meet demand and maintain pressure.
In Hawarden, Sioux County, the city was sandbagging to protect two wells, but is able to meet demand with remaining wells.
In Clay County, the Iowa Lakes Regional Water had one stream crossing washed out. A small portion of the system is without water and those customers will be under a boil advisory after service is restored.
The DNR has received reports of 34 cities, most in northwest Iowa, that have discharged wastewater because of the rainfall. Cedar Rapids was the eastern-most city to report a discharge. Although, it’s likely that more have had discharges as heavy inflow overwhelmed collection and treatment systems.
Cities often intentionally discharge wastewater after intense rainfall to prevent basements from backing up or to protect the treatment plants.
Generally, people and pets should avoid contact with flood waters for at least 24 to 48 hours after flooding ends because bacteria levels could be elevated.
In addition to cities, the DNR has received reports of 19 animal feeding operations with overflows from their settling basins. All have been in the northwest part of the state, from Lyon to Ida counties.
Some of the animal feeding operations have National Discharge Elimination System (NPDES) permits, which allow them to discharge when rainfall exceeds a 25-year, 24-hour rain event. Generally, that’s about 5 inches of rain within 24 hours.
Some operations discharge to protect their manure storage facilities, while others may overflow due to excess storm water runoff. Some livestock producers are pumping to pastures or other basins, making it less likely the effluent will reach a water of the state.
For more information contact Bryon Whiting at 712/260-0925 or 712-262-4177 or Bryon.Whiting@dnr.iowa.gov for northwest Iowa; or Trent Lambert at 641-424-4073 or Trent.Lambert@dnr.iowa.gov for north central Iowa.