Twin Branch
Twin Branch is a gravity dam located in St. Joseph County, Indiana, built in 1903. It carries a High hazard potential classification and has a poor condition assessment.
About Twin Branch
The primary purpose of Twin Branch is hydroelectric. The dam generates hydroelectric power by channeling water through turbines, converting the energy of flowing water into electricity. The dam is owned by Indiana & Michigan Power Company (public utility). It impounds the St Joseph River near Mishawaka.
The dam stands 41 feet tall and stretches 946 feet across, creates a reservoir covering 1,065 acres, has a maximum storage capacity of 10,000 acre-feet, and collects water from a drainage area of 3,530 square miles. Completed in 1903, the structure is over a century old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated poor, meaning the dam has recognized safety deficiencies that require remediation to address risks. An emergency action plan is in place for this dam. The most recent inspection on record was 09/08/2022.
At 41 feet, this dam is taller than 88% of dams nationwide.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Indiana dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Indiana |
| County | St. Joseph |
| Nearest City | Mishawaka |
| River/Stream | St Joseph River |
| Coordinates | 41.66589, -86.13272 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 41 ft |
| Dam Height | 41 ft |
| Dam Length | 946 ft |
| Year Completed | 1903 (123 years old) |
Storage & Hydraulics
| NID Storage | 10,000 acre-ft |
| Max Storage | 10,000 acre-ft |
| Normal Storage | 9,700 acre-ft |
| Surface Area | 1,065 acres |
| Drainage Area | 3,530 sq mi |
| Max Discharge | 37,600 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | Indiana & Michigan Power Company |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Poor |
| Last Inspection | 09/08/2022 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | IN03011 |
| Federal ID | IN03011 |
| More Info | State Dam Safety Program |