Oian Dahl Detention is a privately owned Earth dam in Fillmore, Minnesota, completed in 1992 by the USDA NRCS for the primary purpose of Flood Risk Reduction on the Root River S Branch. With a height of 26 feet and a length of 280 feet, this dam has a storage capacity of 37 acre-feet and a surface area of 2 acres. The dam is regulated by the MNDNR EWR and meets state permitting, inspection, and enforcement requirements.

Despite its low hazard potential and satisfactory condition assessment, Oian Dahl Detention poses a moderate risk level due to its uncontrolled spillway type and outlet gates. The dam has not been modified in recent years and is subject to inspections every 8 years. Emergency action plans and inundation maps have not been prepared, raising concerns about the readiness for potential risks and disasters. The presence of moderate risk underscores the importance of proactive risk management measures for this critical infrastructure in the event of a flooding emergency.