Kehalani Offsite Retention Basin Reservoir Report

Last Updated: December 20, 2025

The Kehalani Offsite Retention Basin, also known as the Wailuku Project District Retention Basin, is a private-owned structure located in Wailuku, Maui, Hawaii.


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Summary

Completed in 2003, this earth dam stands at a height of 30 feet and has a length of 2300 feet. Its primary purpose is flood risk reduction, with a storage capacity of 490 acre-feet and a maximum discharge of 2076 cubic feet per second. The dam is situated on Waikapu Stream and is regulated by the Department of Land and Natural Resources (DLNR) in Hawaii.

Despite its crucial role in mitigating flood risks, the Kehalani Offsite Retention Basin is currently assessed as having a high hazard potential with poor condition. The last inspection in May 2020 indicated the need for improvements, highlighting the importance of proactive maintenance and risk management measures. While it has undergone no modifications since completion, its emergency action plan (EAP) status, including contact information and inundation maps, is currently not up-to-date, raising concerns about its readiness in case of emergencies. As water resource and climate enthusiasts, it is essential to monitor and advocate for the proper maintenance and upkeep of this vital infrastructure to safeguard the surrounding community and environment.

Year Completed

2003

Dam Length

2300

Dam Height

30

River Or Stream

Waikapu Stream

Primary Dam Type

Earth

Surface Area

20

Drainage Area

1.38

Nid Storage

490

Hazard Potential

High

Foundations

Unlisted/Unknown

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.