Plane Nine
Plane Nine is an earth dam located in Blair County, Pennsylvania, built in 1907. It carries a High hazard potential classification and has a fair condition assessment.
About Plane Nine
The primary purpose of Plane Nine 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 Altoona Water Authority (local government). It impounds the Blair Gap Run.
The dam stands 51 feet tall and stretches 735 feet across, creates a reservoir covering 23 acres, has a maximum storage capacity of 561 acre-feet, and collects water from a drainage area of 13 square miles. Completed in 1907, the structure is over a century 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 05/13/2020.
At 51 feet, this dam is taller than 93% 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 Pennsylvania 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 | Pennsylvania |
| County | Blair |
| River/Stream | Blair Gap Run |
| Coordinates | 40.42972, -78.50306 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 51 ft |
| Dam Height | 51 ft |
| Dam Length | 735 ft |
| Year Completed | 1907 (119 years old) |
Storage & Hydraulics
| NID Storage | 561 acre-ft |
| Max Storage | 561 acre-ft |
| Normal Storage | 337 acre-ft |
| Surface Area | 23 acres |
| Drainage Area | 13 sq mi |
Ownership & Safety
| Purpose | Water Supply |
| Owner | ALTOONA WATER AUTHORITY |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Fair |
| Last Inspection | 05/13/2020 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | PA00520 |
| Federal ID | PA00520 |
| More Info | State Dam Safety Program |