Mallard Marsh Dam No 3, located in Cerro Gordo County, Iowa, is a local government-owned structure designed by WALLACE, HOL, KAS&SAHMITT in 1967. This earth dam serves primarily for recreation purposes, with a normal storage capacity of 39 acre-feet and a maximum storage of 129 acre-feet. Situated on the TR-WINNEBAGO RIVER, the dam has a length of 425 feet and a height of 8 feet, with a low hazard potential and a moderate risk assessment rating of 3.

Managed by the Iowa Department of Natural Resources (Iowa DNR), Mallard Marsh Dam No 3 is state-regulated, inspected, and enforced. The dam does not have a spillway and is classified as uncontrolled, with no outlet gates or associated structures. Despite being in a low hazard category, the dam's condition assessment is currently not rated, and there is no available information on emergency action plans or risk management measures. The dam's location in FERTILE, Iowa, offers a surface area of 20 acres and a drainage area of 2.97 square miles, providing valuable recreational opportunities for locals and visitors alike.

Overall, Mallard Marsh Dam No 3 is an important earth dam structure in the St. Paul District, serving as a recreational resource for the community. With its unique design and location on the TR-WINNEBAGO RIVER, the dam plays a crucial role in managing water resources in the area. While the dam's risk assessment is moderate, ongoing monitoring and maintenance by the Iowa DNR ensure the safety and functionality of this vital infrastructure for water resource and climate enthusiasts to explore and appreciate.