Williams Lake Dam Reservoir Report

Last Updated: December 14, 2025

Williams Lake Dam, located in Marlborough, Massachusetts, is a crucial structure owned by the local government and regulated by the Department of Conservation and Recreation.


°F

°F

mph

Wind

%

Humidity

Summary

Built in 1882, this earth dam stands at 11 feet high and spans 270 feet in length, with a primary purpose of water supply for the surrounding area. The dam holds a storage capacity of 767 acre-feet and serves as a key feature on the Assabet River, with a drainage area of 0.45 square miles.

Despite its age, Williams Lake Dam is assessed to be in satisfactory condition, with a high hazard potential due to its location and design. The dam features an uncontrolled spillway type and has a moderate risk assessment rating. Regular inspections are conducted, with the last assessment taking place in August 2015. The dam has not been modified in recent years, and emergency action plans are in place to address any potential risks associated with the structure.

For water resource and climate enthusiasts, Williams Lake Dam offers a glimpse into the historical infrastructure that supports the region's water supply. With a focus on safety and regulatory compliance, the dam continues to play a vital role in managing water resources in Middlesex County. Its location on the Assabet River adds to its significance, making it a key element in the local landscape for both practical and environmental reasons.

Year Completed

1882

Dam Length

270

Dam Height

11

River Or Stream

ASSABET RIVER

Primary Dam Type

Earth

Surface Area

0.41

Hydraulic Height

6

Drainage Area

0.45

Nid Storage

767

Hazard Potential

High

Foundations

Unlisted/Unknown

Nid Height

11
       
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.