Great Stone Reservoir Report
Last Updated: March 19, 2026
Great Stone, also known as Lawrence Dam or Merrimack River Dam, is a historic masonry dam located in Lawrence, Massachusetts.
Summary
Completed in 1848, this dam serves primarily for hydroelectric power generation and recreation purposes, with a height of 38 feet and a length of 943 feet. It holds a storage capacity of 19,900 acre-feet and has a maximum discharge rate of 128,000 cubic feet per second.
Managed by a private owner, this dam is not regulated by the state but falls under the jurisdiction of the Federal Energy Regulatory Commission (FERC). Despite its low hazard potential, the dam has a moderate risk level and undergoes inspections every three years. The spillway is uncontrolled, with a width of 920 feet, and the dam sits on a rock foundation in the Merrimack River, serving as a significant structure in the region's water resource management and climate resilience efforts.
°F
°F
mph
Wind
%
Humidity
15-Day Weather Outlook
Year Completed |
1848 |
Dam Length |
943 |
Dam Height |
38 |
River Or Stream |
Merrimack River |
Primary Dam Type |
Masonry |
Surface Area |
655 |
Drainage Area |
4460 |
Nid Storage |
19900 |
Hazard Potential |
Low |
Foundations |
Rock |
Nid Height |
38 |
Seasonal Comparison
5-Day Hourly Forecast Detail
Nearby Streamflow Levels
Spicket River Near Methuen
|
293cfs |
Merrimack River Bl Concord River At Lowell
|
24500cfs |
Concord R Below R Meadow Brook
|
1880cfs |
Shawsheen River Near Wilmington
|
166cfs |
Spicket River At North Salem
|
62cfs |
Beaver Brook At North Pelham
|
247cfs |
Dam Data Reference
Condition Assessment
SatisfactoryNo 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
HighDams 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.
Great Stone
Wolcott Avenue 57, Lawrence