Arco Dam Reservoir Report

Last Updated: December 9, 2025

Arco Dam, located in Silver Lake, Iowa, was completed in 1968 by the USDA NRCS and is owned and regulated by a private entity.


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Summary

The dam serves multiple purposes, including fire protection and as a small fish pond, with a storage capacity of 233 acre-feet and a surface area of 9 acres. It is situated on the TR-West Branch Little Sioux River and has a low hazard potential, making it a vital resource for the surrounding community.

Managed by the Iowa DNR, Arco Dam is an earth-filled structure with a height of 29 feet and a length of 511 feet. Despite being uncontrolled, the spillway type ensures water release in case of overflow. The dam's risk assessment is moderate, indicating the need for ongoing monitoring and maintenance to ensure its safety and effectiveness in managing water resources in the region.

For water resource and climate enthusiasts, Arco Dam offers a fascinating example of how private entities and state agencies collaborate to manage water infrastructure. With its unique design and multi-purpose functionality, the dam stands as a testament to sustainable water management practices in the region. Its low hazard potential and moderate risk assessment highlight the importance of ongoing inspections and risk management measures to safeguard this critical resource for future generations.

Year Completed

1968

Dam Length

511

Dam Height

29

River Or Stream

TR-WEST BRANCH LITTLE SIOUX

Primary Dam Type

Earth

Surface Area

9

Drainage Area

1.62

Nid Storage

233

Hazard Potential

Low

Foundations

Soil

Nid Height

29
       
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.