Board Talk: Erosion, Sea Level Rise Threaten Sand Island Wastewater Plant Outfall

The stop gate for the Sand Island Wastewater Treatment Plant. Originally built 150 feet from the shoreline, it is now in danger of being inundated by waves.

The Sand Island Wastewater Treatment Plant collects sewage from more than 400,000 residents and visitors in Honolulu and discharges 66 million gallons of effluent a day into the sea via along, wide underground outfall.

The 84-inch-wide outfall extends a mile offshore from a concrete-encased stop gate, which is a kind of valve that can control the effluent flow if necessary.

The problem: That gate . . .

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