Cottonwood Lake is a gravity dam located in Lyon County, Minnesota, built in 1960. It carries a Low hazard potential classification and has a fair condition assessment.
Dam profile
NID height · 9 ft9 ft tall. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic concrete gravity section and the water level is illustrative.
About Cottonwood Lake
The primary purpose of Cottonwood Lake is grade stabilization. Grade stabilization dams prevent erosion by reducing the slope and velocity of water flowing through a channel. They're commonly used to stop gullies from deepening and to protect downstream land and infrastructure. The dam is owned by County of Lyon (private). It impounds the Yellow Medicine River-tr near Hanley Falls.
The dam stands 9 feet tall, creates a reservoir covering 378 acres, has a maximum storage capacity of 3,582 acre-feet, and collects water from a drainage area of 20 square miles. Completed in 1960, the structure is well into its service life at over 50 years old.
This dam has a low hazard potential classification, meaning that failure would cause minimal damage, limited primarily to the dam owner's property, with no expected loss of life. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. The most recent inspection on record was 11/14/2018.
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Location
| State | Minnesota |
| County | Lyon |
| Nearest City | Hanley Falls |
| River/Stream | Yellow Medicine River-tr |
| Coordinates | 44.62193, -95.69174 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 9 ft |
| Dam Height | 9 ft |
| Year Completed | 1960 (66 years old) |
Storage & Hydraulics
| NID Storage | 3,582 acre-ft |
| Max Storage | 3,582 acre-ft |
| Normal Storage | 2,765 acre-ft |
| Surface Area | 378 acres |
| Drainage Area | 20 sq mi |
Ownership & Safety
| Purpose | Grade Stabilization |
| Owner | County of Lyon |
| Owner Type | Private |
| Hazard Classification | Low |
| Condition Assessment | Fair |
| Last Inspection | 11/14/2018 |
| Emergency Action Plan | Not Required |
Identifiers
| NID ID | MN00768 |
| Federal ID | MN00768 |
| More Info | State Dam Safety Program |