Little Seneca Dam
Little Seneca Dam is an earth dam located in Montgomery County, Maryland, built in 1984. It carries a High hazard potential classification and has a fair condition assessment.
About Little Seneca Dam
The primary purpose of Little Seneca 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 Washington Suburban Sanitary Commission (public utility). It impounds the Little Seneca Creek near Germantown.
The dam stands 99 feet tall and stretches 628 feet across, creates a reservoir covering 505 acres, has a maximum storage capacity of 24,185 acre-feet, and collects water from a drainage area of 20 square miles. Completed in 1984, the structure is 42 years 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 fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. Notably, no emergency action plan is currently on file for this high-hazard dam. The most recent inspection on record was 05/30/2024.
At 99 feet, this dam is taller than 98% of all dams in the United States.
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 Maryland 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 | Maryland |
| County | Montgomery |
| Nearest City | Germantown |
| River/Stream | Little Seneca Creek |
| Coordinates | 39.18500, -77.30000 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 99 ft |
| Dam Height | 99 ft |
| Dam Length | 628 ft |
| Year Completed | 1984 (42 years old) |
Storage & Hydraulics
| NID Storage | 24,185 acre-ft |
| Max Storage | 24,185 acre-ft |
| Normal Storage | 13,050 acre-ft |
| Surface Area | 505 acres |
| Drainage Area | 20 sq mi |
| Max Discharge | 73,292 cfs |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Washington Suburban Sanitary Commission |
| Owner Type | Public Utility |
| Hazard Classification | High |
| Condition Assessment | Fair |
| Last Inspection | 05/30/2024 |
| Emergency Action Plan | No |
Identifiers
| NID ID | MD00297 |
| Federal ID | MD00297 |
| More Info | State Dam Safety Program |