Hallowell Swm Dam Reservoir Report

Last Updated: December 5, 2025

Hallowell Swm Dam, located in Montgomery County, Maryland, is a crucial water resource for recreation purposes.


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Summary

Built in 1990, this earth dam stands at a height of 29 feet and spans 600 feet in length. With a storage capacity of 357 acre-feet, the dam serves to regulate the flow of James Creek and offers a surface area of 14.8 acres for outdoor activities.

Managed by the local government and regulated by the Maryland Dam Safety agency, Hallowell Swm Dam has been assessed to be in fair condition with a low hazard potential. The dam features an uncontrolled spillway with a width of 80 feet, capable of managing a maximum discharge of 3800 cubic feet per second. Despite its moderate risk assessment score, the dam has undergone regular inspections, with the last assessment conducted in April 2021.

For water resource and climate enthusiasts, Hallowell Swm Dam presents an interesting case study in dam management and risk assessment. With a focus on recreation, this dam serves as a vital infrastructure for the community while also highlighting the importance of maintaining and monitoring dams to ensure public safety and environmental sustainability. Its location, design details, and regulatory oversight make it a valuable asset in the water resource landscape of Maryland.

Year Completed

1990

Dam Length

600

Dam Height

29

River Or Stream

James Creek

Primary Dam Type

Earth

Surface Area

14.8

Drainage Area

1.2

Nid Storage

357

Hazard Potential

Low

Foundations

Unlisted/Unknown

Nid Height

29
       
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.