Maynes Grove South Dam, located in Cedar Falls, Iowa, is a locally owned earth dam constructed in 1992 by the USDA NRCS. The dam serves primarily for recreational purposes, with a maximum storage capacity of 79 acre-feet and a normal storage level of 50 acre-feet. The dam stands at 29 feet high and spans 335 feet in length, impounding water from the TR-MAYNES CREEK.

The dam, regulated by the Iowa DNR, has a low hazard potential and a moderate risk assessment rating. While the condition of the dam is currently not rated, it is subject to state inspection, permitting, and enforcement. The structure is equipped with an uncontrolled spillway and is located in a scenic setting with a surface area of 5.8 acres. Water resource and climate enthusiasts will find Maynes Grove South Dam an intriguing site for its recreational significance and its role in managing water resources in Franklin County, Iowa.