Union Mill Pond Reservoir Report

Last Updated: December 5, 2025

Union Mill Pond, also known as Pascoag Reservoir Lower, is a privately owned water resource located in Burrillville, Rhode Island.


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Summary

This earth dam, completed in 1883, stands at a height of 7.3 feet and has a maximum storage capacity of 70 acre-feet. With a normal storage level of 45 acre-feet and a drainage area of 9 square miles, this reservoir plays a crucial role in managing water flow and storage in the region.

The dam's spillway width of 26 feet and maximum discharge capacity of 425 cubic feet per second highlight its importance in flood control and water regulation. Even though the condition assessment is marked as "Not Rated" and it has a significant hazard potential, the dam undergoes regular inspections every 5 years to ensure its structural integrity and safety. With the State of Rhode Island regulating and permitting its operations, Union Mill Pond serves as a vital water resource for the community while also posing a unique challenge in managing its risk and potential hazards.

As a site of historical significance and environmental importance, Union Mill Pond stands as a testament to the intersection of human engineering and natural resource management. Water resource and climate enthusiasts can appreciate the complexities involved in maintaining and utilizing this reservoir, as well as the ongoing efforts to balance its benefits with potential risks. With its rich history dating back to the 19th century, this dam continues to play a crucial role in water management and flood control in the Providence County area.

Year Completed

1883

Dam Length

290

Dam Height

7.3

River Or Stream

PASCOAG RIVER

Primary Dam Type

Earth

Surface Area

12

Hydraulic Height

5

Drainage Area

9

Nid Storage

70

Hazard Potential

Significant

Nid Height

7
       
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.