Upper Deckers No. 4 is an earth dam located in Preston County, West Virginia, built in 1966. It carries a High hazard potential classification and has a fair condition assessment.
Dam profile
NID height · 39 ft39 ft tall and 376 ft long, taller than 85% of U.S. dams with a recorded height. Height is drawn to scale against a two-story house, about 25 ft; the profile is a generic embankment section and the water level is illustrative.
About Upper Deckers No. 4
The primary purpose of Upper Deckers No. 4 is flood risk reduction. The dam is designed to control downstream flooding by temporarily storing excess water during storms and releasing it at a controlled rate. The dam is local government-owned. It impounds the Dillan Run near Masontown.
The dam stands 39 feet tall and stretches 376 feet across, creates a reservoir covering 10 acres, has a maximum storage capacity of 932 acre-feet, and collects water from a drainage area of 3 square miles. Completed in 1966, the structure is well into its service life at over 50 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. An emergency action plan is in place for this dam. The most recent inspection on record was 07/31/2025.
At 39 feet, this dam is taller than 85% of dams nationwide.
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 West Virginia 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 | West Virginia |
| County | Preston |
| Nearest City | Masontown |
| River/Stream | Dillan Run |
| Coordinates | 39.52944, -79.77833 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 39 ft |
| Dam Height | 39 ft |
| Dam Length | 376 ft |
| Year Completed | 1966 (60 years old) |
Storage & Hydraulics
| NID Storage | 932 acre-ft |
| Max Storage | 932 acre-ft |
| Normal Storage | 80 acre-ft |
| Surface Area | 10 acres |
| Drainage Area | 3 sq mi |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Flood Risk Reduction |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Fair |
| Last Inspection | 07/31/2025 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | WV07709 |
| Federal ID | WV07709 |
| More Info | State Dam Safety Program |