Rock Run Reservoir Report

Last Updated: December 6, 2025

Rock Run, also known as Coatesville Reservoir, is a private water supply dam located in West Caln Township, Chester County, Pennsylvania.


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Summary

Built in 1917, this concrete dam stands at a height of 42 feet and has a storage capacity of 1,250 acre-feet. The primary purpose of Rock Run is water supply, serving both recreational and domestic needs in the area.

Managed by the Pennsylvania Department of Environmental Protection, Rock Run is subject to state regulations and inspections to ensure its safety and functionality. Despite being classified as having a high hazard potential, the dam's condition assessment is rated as fair, with the last inspection conducted in July 2020. With a surface area of 61 acres and a drainage area of 5.3 square miles, Rock Run plays a crucial role in water resource management in the region.

Rock Run's historical significance and engineering design make it an important site for water resource and climate enthusiasts to study. With its longevity and continued operation, this dam serves as a reminder of the importance of maintaining and managing water infrastructure for both human and environmental needs. As climate change impacts water resources, understanding and monitoring structures like Rock Run become even more critical for sustainable water supply management.

Years Modified

2009 - Other

Year Completed

1917

Dam Length

583

Dam Height

42

River Or Stream

ROCK RUN

Primary Dam Type

Concrete

Surface Area

61

Drainage Area

5.3

Nid Storage

1250

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

42
       
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.