Penallen Reservoir Report

Last Updated: December 6, 2025

Penallen, a privately owned dam located in Horsham Township, Montgomery County, Pennsylvania, plays a crucial role in flood risk reduction along the TR Pennypack Creek.


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Summary

Completed in 1982, this earth dam stands at a height of 11.5 feet and spans 400 feet in length, with a storage capacity of 16 acre-feet. Despite its fair condition assessment, Penallen is classified as having a significant hazard potential, prompting a biennial inspection schedule since its last assessment in 2012.

Managed by the Pennsylvania Department of Environmental Protection, Penallen is subject to state regulation, permitting, inspection, and enforcement to ensure its structural integrity and public safety. The dam has undergone modifications in 2010 to enhance its hydraulic capabilities, contributing to its ongoing flood risk reduction efforts. Additionally, Penallen falls under the jurisdiction of the Baltimore District of the US Army Corps of Engineers, although it is not directly owned or funded by federal agencies.

With its strategic location and vital purpose in mitigating flooding risks, Penallen serves as a key component in protecting the surrounding community and environment. As climate change continues to impact water resources and weather patterns, the maintenance and monitoring of dams like Penallen are essential in safeguarding against potential disasters and ensuring the resilience of water infrastructure in the face of a changing climate.

Years Modified

2010 - Hydraulic

Year Completed

1982

Dam Length

400

Dam Height

11.5

River Or Stream

TR PENNYPACK CREEK

Primary Dam Type

Earth

Drainage Area

0.2

Nid Storage

16

Hazard Potential

Significant

Foundations

Unlisted/Unknown

Nid Height

12
       
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.