Speedwell Dam Reservoir Report

Last Updated: December 9, 2025

Speedwell Dam, located in Morristown, New Jersey, is a picturesque masonry dam built in 1939 along the Whippany River.


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Summary

Owned by the local government, its primary purpose is for recreation, offering a tranquil setting for visitors to enjoy. With a height of 13.5 feet and a storage capacity of 349 acre-feet, the dam spans 145 feet in length and covers a surface area of 20 acres.

Despite its fair condition assessment and high hazard potential, Speedwell Dam is regularly inspected by the New Jersey Department of Environmental Protection to ensure its structural integrity and safety. The dam has a normal storage capacity of 77 acre-feet and a drainage area of 25.2 square miles, with a maximum discharge capacity of 4255 cubic feet per second. The dam's location within Morristown Town provides a vital recreational resource for the community, attracting water resource and climate enthusiasts alike to appreciate its natural beauty and significance.

Additionally, Speedwell Dam falls under the jurisdiction of Congressional District 11 in New Jersey, represented by Mikie Sherrill (D). With its historical significance and ongoing regulatory oversight, Speedwell Dam serves as a key landmark in the region, offering both recreational opportunities and a reminder of the importance of proper dam management in ensuring water resource sustainability and climate resilience.

Year Completed

1939

Dam Length

145

Dam Height

13.5

River Or Stream

Whippany River

Primary Dam Type

Masonry

Surface Area

20

Drainage Area

25.2

Nid Storage

349

Hazard Potential

High

Nid Height

14
       
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.