Three Mile Creek Watershed Site U-4, located in Union County, Iowa, is a locally owned earth dam completed in 1980 by the USDA NRCS. The dam stands at 28 feet high and spans 620 feet, creating a storage capacity of 251 acre-feet for fire protection, livestock use, and small fish pond purposes. Situated on TR-Three Mile Creek, this dam is regulated by the Iowa DNR and falls under state jurisdiction for permitting, inspection, and enforcement.

With a low hazard potential and a moderate risk assessment rating, Three Mile Creek Watershed Site U-4 serves as an essential infrastructure for flood risk reduction in the area. While the condition assessment is not rated, the dam continues to provide valuable water resource management in the region. As a part of the Rock Island District, this site contributes to the overall watershed management efforts and showcases the collaborative efforts of local government and federal agencies in maintaining water infrastructure for the community.