Occoquan Lower Storage Dam is a gravity dam located in Fairfax County, Virginia. It carries a High hazard potential classification and has a satisfactory condition assessment.
Dam profile
NID height · 20 ft20 ft tall and 484 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 Occoquan Lower Storage Dam
The primary purpose of Occoquan Lower Storage 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 Fairfax County Water Authority (local government). It impounds the Occoquan River.
The dam stands 20 feet tall and stretches 484 feet across, creates a reservoir covering 19 acres, has a maximum storage capacity of 170 acre-feet, and collects water from a drainage area of 596 square miles.
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 satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 11/05/2020.
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 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 | Virginia |
| County | Fairfax |
| River/Stream | Occoquan River |
| Coordinates | 38.68960, -77.26900 |
Physical Characteristics
| Dam Type | Gravity |
| NID Height | 20 ft |
| Dam Height | 20 ft |
| Dam Length | 484 ft |
Storage & Hydraulics
| NID Storage | 170 acre-ft |
| Max Storage | 170 acre-ft |
| Normal Storage | 170 acre-ft |
| Surface Area | 19 acres |
| Drainage Area | 596 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | Fairfax County Water Authority |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Satisfactory |
| Last Inspection | 11/05/2020 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | VA153005 |
| Federal ID | VA153005 |
| More Info | State Dam Safety Program |