Green Castle Dam Reservoir Report

Last Updated: December 13, 2025

Green Castle Dam, located in Marshall County, Iowa, is a local government-owned structure on the TR-Brush Creek that serves primarily for recreational purposes.


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Summary

Built in 1954 by CLAPSADDLE-GARBER, this earth dam stands at a height of 30 feet and spans 650 feet in length, with a storage capacity of 263 acre-feet. Despite its uncontrolled spillway type and significant hazard potential, the dam's condition assessment remains satisfactory as of the last inspection in June 2020.

With its location in Ferguson, Iowa, the Green Castle Dam offers a serene setting for water resource and climate enthusiasts to explore. The dam's stone core and soil foundation contribute to its structural integrity, while the surrounding area boasts a surface area of 17 acres and a drainage area of 0.44 square miles. While the dam has not undergone significant modifications over the years, it is subject to regular inspections by the Iowa Department of Natural Resources to ensure compliance with state regulations and enforcement.

In the event of emergencies, the dam's risk assessment is categorized as moderate, with a designated inspection frequency of 5 years. While an Emergency Action Plan (EAP) is not currently prepared, the dam's risk management measures aim to mitigate potential hazards and ensure public safety. Overall, Green Castle Dam stands as a vital recreational asset in the region, showcasing the intersection of water resource management and environmental stewardship.

Year Completed

1954

Dam Length

650

Dam Height

30

River Or Stream

TR- BRUSH CREEK

Primary Dam Type

Earth

Surface Area

17

Drainage Area

0.44

Nid Storage

263

Hazard Potential

Significant

Foundations

Soil

Nid Height

30
       
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.