Grafton is a buttress dam located in Ozaukee County, Wisconsin, built in 1918. It carries a Significant hazard potential classification and has a fair condition assessment.
Dam profile
NID height · 20 ft20 ft tall and 206 ft long. 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 Grafton
The primary purpose of Grafton is recreation. The dam creates a reservoir used for recreational activities such as fishing, boating, and swimming. The dam is owned by Village of Grafton (local government). It impounds the Milwaukee near Grafton.
The dam stands 20 feet tall and stretches 206 feet across, creates a reservoir covering 35 acres, has a maximum storage capacity of 400 acre-feet, and collects water from a drainage area of 451 square miles. Completed in 1918, the structure is over a century old.
This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in 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. An emergency action plan is in place for this dam. The most recent inspection on record was 06/16/2021.
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Location
| State | Wisconsin |
| County | Ozaukee |
| Nearest City | Grafton |
| River/Stream | Milwaukee |
| Coordinates | 43.31885, -87.94920 |
Physical Characteristics
| Dam Type | Buttress |
| NID Height | 20 ft |
| Dam Height | 20 ft |
| Dam Length | 206 ft |
| Year Completed | 1918 (108 years old) |
Storage & Hydraulics
| NID Storage | 400 acre-ft |
| Max Storage | 400 acre-ft |
| Normal Storage | 260 acre-ft |
| Surface Area | 35 acres |
| Drainage Area | 451 sq mi |
| Max Discharge | 15,420 cfs |
| Spillway Type | Controlled |
Ownership & Safety
| Purpose | Recreation |
| Owner | Village of Grafton |
| Owner Type | Local Government |
| Hazard Classification | Significant |
| Condition Assessment | Fair |
| Last Inspection | 06/16/2021 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WI00171 |
| Federal ID | WI00171 |
| More Info | State Dam Safety Program |