Located in Shelby County, Iowa, the Mill Picayune Watershed Site M-22-3 is a significant earth dam completed in 1978 by the USDA NRCS. With a dam height of 37 feet and a length of 550 feet, this structure serves multiple purposes including fire protection, stock, small fish pond, and flood risk reduction. The dam has a storage capacity of 207 acre-feet, with a normal storage volume of 94 acre-feet and a surface area of 10 acres, covering a drainage area of 0.53 square miles.

Managed by the Iowa DNR, this watershed site is state-regulated and undergoes regular inspections to ensure its structural integrity and functionality. Despite being classified as having a significant hazard potential, the condition assessment in 2015 deemed the dam as satisfactory. With its proximity to TR-Mill Creek, the dam plays a crucial role in water resource management and environmental protection in the region. For water resource and climate enthusiasts, the Mill Picayune Watershed Site M-22-3 offers a fascinating case study in dam engineering and watershed management practices.