Elm Lake Dam
Elm Lake Dam is an earth dam located in Brown County, South Dakota, built in 1937. It carries a High hazard potential classification and has a satisfactory condition assessment.
About Elm Lake Dam
The primary purpose of Elm Lake Dam is water supply. The dam stores water for municipal, industrial, or agricultural use, helping ensure a reliable supply for the surrounding area. The dam is owned by S&pl (state). It impounds the Elm River near Westport.
The dam stands 52 feet tall and stretches 1,150 feet across, creates a reservoir covering 1,150 acres, has a maximum storage capacity of 28,800 acre-feet, and collects water from a drainage area of 292 square miles. Completed in 1937, the structure is well-established, with more than 75 years of service.
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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. The most recent inspection on record was 11/22/2022.
At 52 feet, this dam is taller than 93% 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 South Dakota 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 | South Dakota |
| County | Brown |
| Nearest City | Westport |
| River/Stream | Elm River |
| Coordinates | 45.85212, -98.70872 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 52 ft |
| Dam Height | 45 ft |
| Dam Length | 1,150 ft |
| Year Completed | 1937 (89 years old) |
Storage & Hydraulics
| NID Storage | 28,800 acre-ft |
| Max Storage | 28,800 acre-ft |
| Normal Storage | 15,200 acre-ft |
| Surface Area | 1,150 acres |
| Drainage Area | 292 sq mi |
| Max Discharge | 13,850 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | S&PL |
| Owner Type | State |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 11/22/2022 |
Identifiers
| NID ID | SD00328 |
| Federal ID | SD00328 |
| More Info | State Dam Safety Program |