D.F. Riley Grist Mill Dam Reservoir Report
Nearby: Lake Warner Dam Fitzgerald Dam
Last Updated: December 20, 2025
The D.F.
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Summary
Riley Grist Mill Dam, located in Hatfield, Massachusetts, is a historic masonry dam constructed in 1881 along the Mill River. This dam serves a primary purpose of recreation, providing a serene backdrop for outdoor enthusiasts and water resource aficionados alike. With a height of 19 feet and a hydraulic height of 14 feet, the dam holds a storage capacity of 580 acre-feet and covers a surface area of 0.05 square miles.
Despite its historical significance and recreational value, the D.F. Riley Grist Mill Dam is classified as having a significant hazard potential and a poor condition assessment. It is regulated by the Department of Conservation and Recreation in Massachusetts, with state jurisdiction and permitting in place. The dam's inspection frequency is every 5 years, with the most recent assessment in May 2018 revealing the need for maintenance and potential risk management measures.
Climate and water resource enthusiasts are drawn to the D.F. Riley Grist Mill Dam not only for its historical charm but also for the conservation efforts required to maintain its integrity. With a moderate risk assessment rating and a need for improvements in condition, this dam represents a focal point for balancing the preservation of natural resources with the safety and recreational opportunities it provides to the local community and visitors.
Year Completed |
1881 |
Dam Length |
200 |
Dam Height |
19 |
River Or Stream |
MILL RIVER |
Primary Dam Type |
Masonry |
Surface Area |
0.05 |
Hydraulic Height |
14 |
Drainage Area |
47.5 |
Nid Storage |
580 |
Hazard Potential |
Significant |
Foundations |
Unlisted/Unknown |
Nid Height |
19 |
Seasonal Comparison
Weather Forecast
Nearby Streamflow Levels
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.
D.F. Riley Grist Mill Dam