Grand Lake St. Marys - East Embankment Reservoir Report
Last Updated: December 19, 2025
Grand Lake St.
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Summary
Marys - East Embankment, located in St. Marys, Ohio, is a state-regulated dam built in 1841 with a primary purpose of recreation. The dam is an earth type structure standing at a height of 17.9 feet and spanning 7980 feet in length. It boasts a storage capacity of 62,194 acre-feet, supporting a surface area of 13,981 acres and draining a 110.3 square mile watershed.
Managed by the Department of Natural Resources, the dam has a high hazard potential but is currently rated in fair condition as of the last assessment in November 2019. While the dam has not undergone recent modifications, it is subject to regular state inspections and enforcement measures to ensure public safety. With its outlet leading to the Miami and Erie Canal Feeder, the dam serves as a vital component of the local water resource infrastructure, offering both recreational opportunities and flood control benefits to the surrounding community.
Grand Lake St. Marys - East Embankment stands as a historic landmark in Auglaize County, Ohio, designed by John H. Irwin. With its scenic surroundings and important role in water management, the dam continues to be a focal point for water resource and climate enthusiasts interested in the intersection of human infrastructure and natural ecosystems.
Year Completed |
1841 |
Dam Length |
7980 |
Dam Height |
17.9 |
River Or Stream |
OUTLET TO MIAMI AND ERIE CANAL FEEDER |
Primary Dam Type |
Earth |
Surface Area |
13981 |
Drainage Area |
110.3 |
Nid Storage |
62194 |
Hazard Potential |
High |
Nid Height |
18 |
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.
Grand Lake St. Marys - East Embankment