HARTINGTON — The new flood control dam in the southwest portion of Hartington that was completed in 2014 was put to its first real test Sunday.
Three-and-one-half inches of rain fell within an eight-hour period in Hartington.
The high hazard dam is built for a 500-year rain that amounts to eight-inches of rain in a 24-hour period, but it can withstand even higher amounts of rain to prevent the dam from collapsing under water pressure.
The system was designed so if the seven-foot water level vent can’t keep up with the water intake into the dam from above, a safety water vent is positioned at 10-feet, which will release more water through the system. It keeps the water from flowing over the overflow on the east side of the dam and also assures the dam will not break through under water pressure that a 10-12 inch rain could render.
“The entire flood control system is designed and built to hold and release water at a level that the downstream flow can handle without causing serious flooding,” said Dan Kathol, who was the Project Coordinator on the Water Quality and Flood Control project when the dam was built.
“The dam was built out of necessity to prevent serious flooding of businesses, homes and Hwy 57,” Kathol said. “With more homes and industry upstream, and that will continue to increase into the future, Hartington needed a storm water control system that can manage this increase and faster flow of rain and spring snow thaw that will be occurring.
Kathol said if recent occurrences are any indicator, “future weather events could be more severe and we need a system in place to handle the unpredictable nature of large rainstorms or a significant spring snow thaw,” he said.
The pictures above depict how the flood control system works. First, the water accumulates in the large pond upstream from the dike and when it reaches a water level of 7’ in the pond, the water discharges through a vented pipe and out the 36” tube pictured below in photo 1.
The water than flows into a large detention pond which empties out past a concrete wall that has holes allowing the water to empty out at a calculated flow rate to control the water stream that then passes by the assisted living and nursing home facilities as seen in photos 2 and 3. The water flows east from Hwy 57 one block before it enters the underground storm sewer that runs under the city and eventually dumps out into the Norweigen Bow Creek that is located in the northeast part of Hartington.