Potomac River Dam #4
Potomac River Dam #4 is a gravity dam located in Washington County, Maryland, built in 1869. It carries a Significant hazard potential classification.
About Potomac River Dam #4
The primary purpose of Potomac River Dam #4 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 Doi Nps (federal). It impounds the Potomac River near Williamsport, Md.
The dam stands 20 feet tall and stretches 715 feet across, creates a reservoir covering 675 acres, has a maximum storage capacity of 6,750 acre-feet, and collects water from a drainage area of 5,900 square miles. Completed in 1869, the structure is one of the older dams in the region, with over a century and a half of service.
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. An emergency action plan is in place for this dam. The most recent inspection on record was 07/26/2023.
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Location
| State | Maryland |
| County | Washington |
| Nearest City | Williamsport, Md |
| River/Stream | Potomac River |
| Coordinates | 39.49413, -77.82692 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 20 ft |
| Dam Height | 20 ft |
| Dam Length | 715 ft |
| Year Completed | 1869 (157 years old) |
Storage & Hydraulics
| NID Storage | 6,750 acre-ft |
| Max Storage | 6,750 acre-ft |
| Surface Area | 675 acres |
| Drainage Area | 5,900 sq mi |
| Max Discharge | 1,000,000 cfs |
Ownership & Safety
| Purpose | Hydroelectric |
| Owner | DOI NPS |
| Owner Type | Federal |
| Hazard Classification | Significant |
| Condition Assessment | Not Available |
| Last Inspection | 07/26/2023 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | MD00078 |
| Federal ID | MD00078 |
| More Info | State Dam Safety Program |