Plane Nine Reservoir Report

Last Updated: December 5, 2025

Located in Juniata Township, Pennsylvania, Plane Nine is a crucial earth dam built in 1907 for water supply purposes along the Blair Gap Run.


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Summary

Standing at a height of 51 feet and stretching 735 feet in length, this dam has a storage capacity of 561 acre-feet, with a normal storage level of 337 acre-feet. Despite its fair condition assessment, Plane Nine is classified as having a high hazard potential, highlighting the importance of regular inspections and maintenance to ensure the safety of the surrounding community and the efficient management of water resources.

Under the jurisdiction of the Pennsylvania Department of Environmental Protection, Plane Nine is subject to state regulations for permitting, inspection, and enforcement. The dam's primary source agency is the state of Pennsylvania, reflecting the local government's responsibility for its operation and maintenance. With a drainage area of 13.4 square miles and a surface area of 23 acres, Plane Nine plays a vital role in water resource management in Blair County, serving as a key infrastructure for water supply in the region.

As climate change continues to impact water availability and quality, the maintenance and monitoring of dams like Plane Nine are essential for sustainable water management. With a focus on water supply and a history dating back over a century, Plane Nine stands as a testament to the importance of investing in infrastructure resilience and adaptive strategies to address the challenges posed by a changing climate.

Year Completed

1907

Dam Length

735

Dam Height

51

River Or Stream

BLAIR GAP RUN

Primary Dam Type

Earth

Surface Area

23

Drainage Area

13.4

Nid Storage

561

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

51
       
Seasonal Comparison

Weather Forecast

Dam Data Reference

Condition Assessment

Satisfactory
No existing or potential dam safety deficiencies are recognized. Acceptable performance is expected under all loading conditions (static, hydrologic, seismic) in accordance with the minimum applicable state or federal regulatory criteria or tolerable risk guidelines.
Fair
No existing dam safety deficiencies are recognized for normal operating conditions. Rare or extreme hydrologic and/or seismic events may result in a dam safety deficiency. Risk may be in the range to take further action. Note: Rare or extreme event is defined by the regulatory agency based on their minimum
Poor A dam safety deficiency is recognized for normal operating conditions which may realistically occur. Remedial action is necessary. POOR may also be used when uncertainties exist as to critical analysis parameters which identify a potential dam safety deficiency. Investigations and studies are necessary.
Unsatisfactory
A dam safety deficiency is recognized that requires immediate or emergency remedial action for problem resolution.
Not Rated
The dam has not been inspected, is not under state or federal jurisdiction, or has been inspected but, for whatever reason, has not been rated.
Not Available
Dams for which the condition assessment is restricted to approved government users.

Hazard Potential Classification

High
Dams assigned the high hazard potential classification are those where failure or mis-operation will probably cause loss of human life.
Significant
Dams assigned the significant hazard potential classification are those dams where failure or mis-operation results in no probable loss of human life but can cause economic loss, environment damage, disruption of lifeline facilities, or impact other concerns. Significant hazard potential classification dams are often located in predominantly rural or agricultural areas but could be in areas with population and significant infrastructure.
Low
Dams assigned the low hazard potential classification are those where failure or mis-operation results in no probable loss of human life and low economic and/or environmental losses. Losses are principally limited to the owner's property.
Undetermined
Dams for which a downstream hazard potential has not been designated or is not provided.
Not Available
Dams for which the downstream hazard potential is restricted to approved government users.