Blue Marsh Dam Reservoir Report

Last Updated: December 6, 2025

Blue Marsh Dam, located in Reading, Pennsylvania, was completed in 1977 by the US Army Corps of Engineers for the primary purpose of flood risk reduction.


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Summary

Standing at a structural height of 100 feet and with a hydraulic height of 94 feet, the dam plays a crucial role in protecting downstream communities such as Reading, Birdsboro, Pottstown, and Philadelphia from potential flooding events. With a storage capacity of 129,900 acre-feet and a drainage area of 175 square miles, the dam can handle a maximum discharge of 70,000 cubic feet per second.

Despite being classified as having a "Moderate" risk level, the US Army Corps of Engineers implements rigorous risk management measures to ensure the safety and stability of Blue Marsh Dam. Regular inspections, monitoring, and maintenance are conducted to identify any signs of deterioration or potential issues. Emergency repair materials are stocked nearby in case of dam seepage, and staff closely monitor weather forecasts to prepare for possible flood events. Additionally, the Corps collaborates with state and county emergency management officials to conduct emergency exercises and ensure a coordinated response in case of an emergency.

The risk assessment for Blue Marsh Dam is based on the potential for the reservoir level to rise high enough during intense rainfall events, potentially causing erosion that could lead to a breach and subsequent flooding downstream. By closely monitoring the dam's performance and implementing proactive measures, the US Army Corps of Engineers is dedicated to safeguarding the surrounding communities and ensuring the structural integrity of Blue Marsh Dam.

Year Completed

1977

Dam Length

1775

River Or Stream

TULPEHOCKEN CREEK

Primary Dam Type

Rockfill

Surface Area

1147

Hydraulic Height

94

Drainage Area

175

Nid Storage

129900

Structural Height

100

Outlet Gates

Slide (sluice gate) - 0

Hazard Potential

High

Nid Height

100
       
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.