Olson-Agassiz is a local government-owned dam located in Hadler, Minnesota, along the Spring Creek-TR river. Built in 1983 by Houston Eng, this earth dam stands at a height of 17 feet and stretches 4400 feet in length. Its primary purpose is flood risk reduction, with a storage capacity of 2500 acre-feet and a drainage area of 36 square miles.

With a significant hazard potential and a satisfactory condition assessment as of May 2014, Olson-Agassiz is regulated by the Minnesota Department of Natural Resources, with state permitting, inspection, and enforcement in place. While the dam has a moderate risk assessment rating of 3, it is crucial for flood control in the region. The dam's spillway is uncontrolled, with a maximum discharge capacity of 7000 cubic feet per second, making it a vital structure for water resource management in Norman County.