City officials have made progress at turning a mountain into a molehill — the mountain being Oahu’s mammoth heap of trash. But the fact remains that there will always be excess material, and the need to stow it someplace.

Members of the community know this only too well, especially those on the Waianae Coast. That’s where the Waimanalo Gulch Sanitary Landfill has languished, despite the clamor from neighbors to find another location.

The issue burst back into the news in recent weeks when the Honolulu Planning Commission recommended allowing the landfill to remain in the gulch until it reaches capacity. That could be 20 years from now, officials said, but the commission wants to know where the replacement landfill will be, in less than five years.

The state Land Use Commission (LUC) will take up the issue for a final decision, sometime after the written recommendation is transmitted May 1. It’s a controversy — a standoff — that draws sympathy, if not the actual solution, from people living elsewhere.

One is Pamela Nakagawa, whose home is in Pacific Heights. She wrote a letter to the Honolulu Star-Advertiser a few days after the commission’s vote on March 1. And last week, when contacted again, she still exuded passionate support for Waianae.

“My point is, everyone makes garbage, trash, everyone has sewage, everyone has waste of some kind,” she said in a telephone interview. “Why do they come up with just one area on this island that handles that mess? It comes from everywhere.”

The Planning Commission action broke a long silence surrounding the whole issue and it seems determined to keep the conversation going now.

“For the longest time there was nothing,” said its chairman, Dean Hazama. “We never discussed it. Never talked about. Never came up.”

Hazama added that the panel is determined to push the city to fulfill the mandate of finding a replacement site.

Here are the principal conditions it recommended:

>> The city must select an alternate site by the end of 2022. That date is more than a decade after the original deadline of July 31, 2012, for ending regular municipal solid waste deliveries to Waimanalo Gulch. The LUC had set that deadline, but the state Supreme Court struck it down in May 2012.

>> Status reports on the search must go to the Planning Commission every six months, instead of annually.

Lori Kahikina is director of the city Department of Environmental Services. She defended the agency against criticism that the search had not progressed since a committee delivered a list of 11 candidate sites in 2012.

R.M. Towill Corp. helped produce the list following a series of meetings to gather “community-based feedback,” Kahikina said. But part of its contract with the city includes the production of a more technical report to evaluate the sites more fully. That, she said, should be in the city’s hands by the end of this year.

Some of the recommended sites could be eliminated as unsuitable after the study is done. For example, a site might be served by roads unsuited to the frequent traffic of trash trucks, because of its condition or other factors, Kahikina added.

“Some of the other sites recommended belong to the military,” she said, “and it takes an act of God to get permission.”

While the city presses on with that mission, Kahikina underscored the drastic reduction in what’s taken to the landfill as good news worth celebrating.

The most recent effort to winnow the landfilled trashpile further will start Monday when, the city announced last week, all combustible items will be directed to the HPOWER garbage-to-energy plant via the city’s convenience centers. Households may only deliver limited amounts of inert material — such as dirt, rock, sand, gravel and concrete — to Waimanalo Gulch.

The landfill still takes ash residue from HPOWER, but the rest of the municipal solid waste (MSW) load has plummeted. Where 277,000 tons of MSW was landfilled in 2011, in fiscal year 2016 that amount dropped to 62,000 tons, Kahikina said.

That’s because HPOWER’s third boiler was installed in 2015, one capable of incinerating sewage sludge mixed with bulky items — mattresses, furniture and other items that once went to the landfill.

The majority of what’s left is what’s called automotive shredder residue (ASR), the nonmetals that are left when cars are recycled. Putting that in a boiler, too, would require a change in the permit from the state Department of Health, Kahikina said. And the city would need a solution to an operational problem, she said: The ASR burns too hot and can destroy the metal grates of the boiler.

Assuming that can be solved, there’s just the ash from incineration, she said.

“If we can find a reuse for the ash, we could be golden,” Kahikina said.

The city is watching two ash-processing technologies: one by the Dutch company Inashco, which converts ash into aggregate materials, and Lab USA, based in Green Bay, Wis., which processes ash to recover metals.

The challenge is whether either prospective contractor could handle both the inert “bottom ash” as well as the “fly ash,” which can contain toxic elements, Kahikina said. Currently, both types of ash are mixed and encapsulated in a lined cell within the landfill acreage, she said.

Even if all of this can be reduced to virtually nothing, however, the HPOWER permit still requires a landfill for backup, Kahikina said. There must be a place to handle debris in the event of a natural disaster and for boiler shutdowns, whether scheduled for regular maintenance or due to an unforeseen problem, she said.

The state Health Department regulates all of this (see sidebar for a list of what types of refuse require special handling). Steve Chang, the Solid and Hazardous Waste Branch chief, said the department had permitted the ash to be used as an overnight cap for each day’s load of unincinerated trash in the landfill. The aim was to ensure that any hazardous chemicals would not leach into the groundwater.

“We had to impose special conditions on how to handle it,” Chang said. “You don’t want that blowing off, going into the communities, that would be horrible. And if the workers work in that, they kick it up and get it on their clothes and bring it home.”

Ultimately the city opted instead to use tarps to cover the trash layer, removed the next day, he said. The ash, a mix of bottom and fly ash, is encapsulated in a lined cell within the landfill acreage.

As promising as all the progress seems to be, onlookers such as Nakagawa likely won’t be won over until a new landfill site is found — someplace other than in Waianae.

“They’ve been talking for years about putting it elsewhere, but they have not done that,” she said. “And for them to be OK with that, that’s what really bothers me.”