Maunaolu Reservoir
Maunaolu Reservoir is an earth dam located in Honolulu County, Hawaii, built in 1966. It carries a High hazard potential classification and has a fair condition assessment.
About Maunaolu Reservoir
The primary purpose of Maunaolu Reservoir is irrigation. The dam stores and diverts water for agricultural irrigation, supporting farming operations in the surrounding area. The dam is owned by Honolulu Board Of Water Supply (local government). It impounds the Diversion - Glover Tunnel near Makaha.
The dam stands 27 feet tall and stretches 800 feet across, creates a reservoir covering 2 acres, and has a maximum storage capacity of 23 acre-feet. Completed in 1966, the structure is well into its service life at over 50 years old.
This dam carries a high hazard potential classification, which means that a failure or uncontrolled release of water would likely cause loss of human life. This classification reflects the consequences of failure, not the likelihood — it indicates that people live or work in the area downstream. Its condition is rated fair — the dam has minor deficiencies that are being addressed or do not pose an immediate safety threat. An emergency action plan is in place for this dam. The most recent inspection on record was 06/06/2024.
Living Downstream
If you live or work downstream of this dam, consider taking these steps: learn your local evacuation routes, check whether your county emergency management office has a dam failure inundation map, and sign up for local emergency alerts. The Hawaii dam safety program can provide more specific information about emergency planning for this structure.
Search for dams near your address to see all dams in your area with hazard classifications and safety data.
Location
| State | Hawaii |
| County | Honolulu |
| Nearest City | Makaha |
| River/Stream | Diversion - Glover Tunnel |
| Coordinates | 21.48619, -158.18995 |
Physical Characteristics
| Dam Type | Earth |
| NID Height | 27 ft |
| Dam Height | 27 ft |
| Dam Length | 800 ft |
| Year Completed | 1966 (60 years old) |
Storage & Hydraulics
| NID Storage | 23 acre-ft |
| Max Storage | 23 acre-ft |
| Normal Storage | 18 acre-ft |
| Surface Area | 2 acres |
| Spillway Type | Uncontrolled |
Ownership & Safety
| Purpose | Irrigation |
| Owner | Honolulu Board of Water Supply |
| Owner Type | Local Government |
| Hazard Classification | High |
| Condition Assessment | Fair |
| Last Inspection | 06/06/2024 |
| Emergency Action Plan | Yes |
Identifiers
| NID ID | HI00149 |
| Federal ID | HI00149 |
| More Info | State Dam Safety Program |