Honolulu Board of Water Supply Manager and Chief Engineer Ernie Lau has rejected Honolulu Mayor Rick Blangiardi’s request to locate the city’s next solid-­waste landfill in an area where a chemical leak might foul the island’s water resources.

In a recent letter to the city, Lau said he was exercising his authority to deny the request because each of the city’s six proposed landfill sites is located over the island’s aquifer system.

Oahu’s aquifer, generally located in the interior of the island, is delineated by the Board of Water Supply’s No Pass Zone, a region of agency oversight regarding any form of sewage system.

“Never has the importance of this groundwater aquifer been more apparent, and never has our responsibility to protect it been more paramount,” Lau wrote in the letter.

Under the board’s rules, the city has the right to a reconsideration hearing. If the manager still denies the request, the city may appeal to the BWS board within 30 days of a final decision.

Blangiardi spokesman Ian Scheuring on Wednesday said the administration is still evaluating its next move.

The city faces an end-of-year deadline to name a landfill site by order of the state Land Use Commission. The new dump would replace the island’s only municipal landfill, at Waimanalo Gulch on the West side of Oahu.

Blangiardi and Roger Babcock, director of the city Department of Environmental Services, came to the board’s October meeting looking for clarification on the semi-autonomous agency’s authority in the No Pass Zone.

They told the board that the technology exists to prevent a modern landfill’s chemical-laced rainwater, or leachate, from percolating into the groundwater.

Board members said they would consider the request at a specially arranged meeting and suggested that they might even form a subcommittee to take a closer look at it. But further investigation into the board’s rules apparently clarified that the manager has the authority to consider such requests first.

In his letter, Lau said the people of Oahu are still coping with what the state Department of Health described as “a humanitarian and environmental disaster” caused by fuel releases from the U.S. Navy’s Red Hill Bulk Fuel Storage Facility.

According to Navy reports, some 180,000 gallons of various types of fuel have leaked from the 80-year-old Red Hill facility over the decades, including 27,000 gallons of jet fuel in 2014 and 19,000 gallons of jet fuel in May 2021. The last spill led to contaminated tap water in military housing and elsewhere in the Navy’s water system as well as the shutdown of several BWS water sources.

“This unfortunate environmental catastrophe is a stark reminder that we all need to be proactive in protecting all of our precious drinking water resources from underground sources of contamination. Oahu’s aquifer cannot be replaced,” Lau said.

And while modern landfill design and engineering can attempt to reduce the risk of contaminant leakage, Environmental Protection Agency studies and the U.S. Geological Survey have concluded that all landfills eventually leak into the environment and represent a potentially serious problem, he wrote.

The landfill request is listed as an informational item on Monday’s Honolulu Board of Water Supply board of directors meeting at 4 p.m.

The city’s Landfill Advisory Committee, appointed by Blangiardi, decided not to recommend any of the six candidate sites after being briefed by Lau and BWS Deputy Manager Erwin Kawata this summer.

All of the proposed sites — in pockets of Central Oahu and near the North Shore region — are in the No Pass Zone.

Babcock said city plans to go well beyond what is required to safeguard drinking water supplies.

The standard EPA-required protection for a Class D solid-waste landfill is a protective liner that includes a clay-based liner and a thick plastic liner in addition to a collection system that allows for the safe removal of leachate.

But the city’s plan, he said, is to double the liner systems to provide the same level of protection that would be required of a Class C hazardous-waste landfill.

Ann Wright, a retired U.S. Army colonel and member of the Oahu Water Protectors grassroots group, said Honolulu would be asking for trouble if it put a landfill above the island’s aquifer.

“While I understand that no one would want a landfill in their neighborhood, I would certainly hope that no one wants the possibility of a leaking landfill to contaminate our source for drinking water, particularly after the disaster we have endured from the Red Hill jet fuel contamination of this past year — and probably over the years,” Wright said.

In his letter, Lau urged the city to explore new landfill sites below the No Pass Zone and suggested that it request additional time from the Land Use Commission to explore those options.