St. Henry Wwt Lagoon

St. Henry Wwt Lagoon is an earth dam located in Mercer County, Ohio, built in 1988. It carries a Significant hazard potential classification and has a satisfactory condition assessment.

About St. Henry Wwt Lagoon

The primary purpose of St. Henry Wwt Lagoon is tailings. Tailings dams contain waste material from mining operations — typically a slurry of finely ground rock left over after valuable minerals have been extracted. These structures require ongoing monitoring because tailings can contain heavy metals and other contaminants. The dam is owned by Village Of St. Henry (local government). It impounds the Coldwater Creek - Offstream near Coldwater.

The dam stands 27 feet tall and stretches 5,540 feet across, creates a reservoir covering 45 acres, has a maximum storage capacity of 501 acre-feet, and collects water from a drainage area of 0 square miles. Completed in 1988, the structure is 38 years old.

This dam has a significant hazard potential classification, meaning that a failure could cause significant economic damage — flooding roads, bridges, or property downstream — but is not expected to result in loss of life. Its condition is rated satisfactory, indicating no existing or potential dam safety deficiencies are recognized. An emergency action plan is in place for this dam. The most recent inspection on record was 11/07/2024.

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Significant HazardSatisfactory ConditionEmergency Action Plan: Yes

Location

StateOhio
CountyMercer
Nearest CityColdwater
River/StreamColdwater Creek - Offstream
Coordinates40.43000, -84.62444

Physical Characteristics

Dam TypeEarth
NID Height27 ft
Dam Height27 ft
Dam Length5,540 ft
Year Completed1988 (38 years old)

Storage & Hydraulics

NID Storage501 acre-ft
Max Storage501 acre-ft
Normal Storage395 acre-ft
Surface Area45 acres
Drainage Area0 sq mi
Max Discharge20 cfs

Ownership & Safety

PurposeTailings
OwnerVillage of St. Henry
Owner TypeLocal Government
Hazard ClassificationSignificant
Condition AssessmentSatisfactory
Last Inspection11/07/2024
Emergency Action PlanYes

Identifiers

NID IDOH02727
Federal IDOH02727
More InfoState Dam Safety Program

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