Great Falls Dam, Lock No. 20 is a masonry dam located in Montgomery County, Maryland, built in 1850. It carries a Low hazard potential classification.
Dam profile
NID height · 8 ft8 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 Great Falls Dam, Lock No. 20
The primary purpose of Great Falls Dam, Lock No. 20 is navigation. The dam maintains water levels sufficient for boat and barge traffic, supporting commercial or recreational navigation on the waterway. The dam is owned by US Army Corps of Engineers,washington Aqueduct Div (federal). It impounds the C&o Canal.
The dam stands 8 feet tall, and has a maximum storage capacity of 51 acre-feet. Completed in 1850, the structure is one of the older dams in the region, with over a century and a half of service.
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. The most recent inspection on record was 09/30/1996. That was over 30 years ago.
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Location
| State | Maryland |
| County | Montgomery |
| River/Stream | C&o Canal |
| Coordinates | 39.00169, -77.24927 |
Physical Characteristics
| Dam Type | Masonry |
| NID Height | 8 ft |
| Dam Height | 8 ft |
| Year Completed | 1850 (176 years old) |
Storage & Hydraulics
| NID Storage | 51 acre-ft |
| Max Storage | 51 acre-ft |
Ownership & Safety
| Purpose | Navigation |
| Owner | US Army Corps of Engineers,washington Aqueduct Div |
| Owner Type | Federal |
| Hazard Classification | Low |
| Condition Assessment | Not assessed |
| Last Inspection | 09/30/1996 |
| Emergency Action Plan | No |
Identifiers
| NID ID | MD00410 |
| Federal ID | MD00410 |
| More Info | State Dam Safety Program |