by Andrew Walden
In the real world, when a dam nears capacity, a spillway allows water to flow quickly off the top of the reservoir to prevent it from overflowing.
But this is Hawaii.
In Hawaii 124 of the state’s 133 dams are deemed ‘at High Hazard Potential’ by the National Inventory of Dams, a database maintained by the U.S. Army Corps of Engineers and the Association of State Dam Officials. This is the highest proportion of 'High Hazard’ dams of any state.
Video: Diver jumps from Nuuanu Reservoir spillway siphon when water is 60 feet lower than it was today. "Nu'uanu Reservoir was built between 1890-1910. Four reservoirs were built, one with a water tower (picture above) to control water levels."-- Venture Hawaii
So when the Nuuanu Reservoir this morning comes within five feet of cresting over the earthen banks and within 1.5 feet of being able to flow out of the spillway, the BWS and the Caldwell administration panic. 10,000 nearby residents are warned they may have to evacuate--then un-warned. Pumps and fire trucks are dispatched to the reservoir to draw down the water with fire hoses before it reaches the spillway.
Is this an indication that BWS and DLNR believe the dam cannot withstand a full load and that the existing spillway is too high to safely release water given what is apparently a weakened condition for the dam? Is something else wrong with the spillway?
Flashback Kaloko Reservoir, Kauai, 2006, 8 dead: “The state believes Pflueger altered a key safety feature for the dam known as a spillway.”
Here are the communications from BWS and the Mayor’s office this morning:
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BOARD OF WATER SUPPLY MONITORING NU‘UANU DAM 1 - Storm activity has filled dam to near capacity.
from Mayor Caldwell, via FaceBook, 09/13/2018 10:05 AM
The Board of Water Supply’s (BWS) Nu‘uanu Dam #1 is about a 1.5 feet below the spillway due to the amount of rain brought on by former Tropical Storm Olivia.
BWS has been monitoring and siphoning the excess water from the reservoir since the beginning of the week to keep the water level below the spillway. However, with the passing of Olivia, the rain exceeded the siphoning capacity. BWS and Honolulu Fire Department personnel are currently deployed at the dam with water pumps to bring the level of the reservoir down further.
BWS is working with the Mayor’s Office and the Department of Emergency Management to coordinate the operations plan, which includes public evacuation notification and sheltering if needed.
Approximately 10,000 residents would be affected. More information to come as it becomes available.
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VIDEO: With Caldwell at Global Warming Confab in San Francisco, Acting Mayor Amemiya and BWS Officials discuss Nu'uanu Dam 1
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from Mayor Caldwell, via FaceBook, 09/13/2018 1:47pm
"In the very unlikely event that the dam should overflow and an evacuation be deemed necessary, here’s an image of the Nu’uanu Dam evacuation map. Water level is currently receding, and an evacuation is highly unlikely."