The city is moving forward with a controversial plan to expand the Waimanalo Gulch landfill in Leeward O'ahu, even as long-stalled proposals to dump some of O'ahu's trash on the Mainland are quietly clearing some hurdles.

Companies have offered for years to ship O'ahu garbage to huge landfills in rural Washington or Idaho, but the city has rejected them as too expensive and too dependent on resources it has no control over.

But two new federal studies say trash shipments to Washington would pose low risks of environmental harm and pest contamination if handled appropriately. Federal approval is still under review.

The city is not offering a contract for Mainland trash disposal, and has no immediate plans to do so, city spokesman Bill Brennan said.

But a comprehensive waste management plan for O'ahu is scheduled to be completed in March, he said.

"We're looking at the whole big solid waste picture," Brennan said.

Some, like Leeward City Councilman Todd Apo, want the administration to seriously consider shipping trash away. Apo says the city has been slow to look at other alternatives.

Companies hoping for a lucrative deal with the city or private trash collectors have told the U.S. Department of Agriculture that they want to compress rubbish into bundles wrapped in air-tight plastic, then haul it on barges across more than 2,000 miles of ocean.

The barges would be towed up the Columbia River to the port of Roosevelt, Wash., where the garbage would be loaded onto trucks and hauled to the 2,500-acre Roosevelt Regional Landfill, the state's largest dump.

Unless a barge were to capsize, the pollution risks would be minimal, according to an environmental assessment by the USDA's Animal and Plant Health Inspection Service.

And the barges would travel too slowly to pose much risk of colliding with whales or sea turtles, according to the report, completed last month.

A second study by the agency found that the risk of introducing insects or other pests to Washington would be "insignificant" because pests would suffocate in the air-tight garbage bales or be killed by the change in climate.

Two Washington companies with competing proposals for taking O'ahu's garbage are Pacific Rim Environmental Resources and Hawaiian Waste Systems.

A third company, Idaho Waste Systems, had proposed to ship trash to Longview, Wash., then haul it on trains to the Simco Regional Landfill, near Boise, Idaho. The new studies did not address that option.

Honolulu officials contend that the Waimanalo Gulch dump, which has been in operation since 1989, can be expanded for at least 15 more years. Its state permit for the acceptance of municipal solid waste expires in May, 2008.

Foul odors and wind-blown trash from the city-owned dump have been major sore points for some Leeward residents and for the expanding Ko Olina resort, located directly across Farrington Highway.

Apo, who represents the Wai'anae Coast, said the administration should look more seriously at the shipping option.

"I've always believed that shipping the waste out, now that it's allowed by the federal agency that regulates that, is something we need to look at as an alternative to what we are doing," he said.

Apo has visited both the Washington and Idaho sites. "They are places where we should be siting landfills — they're in the middle of nothing and they're some great operations."

He cited the sometimes heated debate between communities that went on several years ago over where to site a new landfill as an example of how sensitive the issue is. "If that didn't wake up everybody and say, 'Hey look, landfills are not the right thing to be doing with our waste in an island environment,' we need to have that message."

Apo said he and other council members have been frustrated that a request for proposals for alternative disposal technologies, which was supposed to have been issued more than a year ago, was recently delayed again.

"That RFP was supposed to provide the city with some guidance as to what kind of alternatives we had to landfilling," he said.

Between the shipping and alternative technologies, Apo said, "my belief is that we can get to a point where we don't need a daily landfill."

Jeff Mikulina, director of the Sierra Club's Hawai'i chapter, said his organization has consistently opposed shipping waste out-of-state.

An amendment to the City Charter approved by O'ahu voters this month requires the city's environmental services director to set up comprehensive curbside recycling, he said.

And while that amendment does not set a date for such a program to be in place, Mikulina believes it provides less of an argument for those calling for trash to be shipped away.

"Potentially, we can do a lot with just curbside recycling, plus either composting or green waste collection and that's what other cities have done pretty well," Mikulina said.

"We don't think it makes sense to send our trash overseas to the Mainland or elsewhere," he said. "We don't think that's the kind of aloha we want to send to the Mainland."

The city and private trash haulers deposit about 300,000 tons of waste in Waimanalo Gulch every year. Fees that private haulers pay to use the facility help finance the city's collection of residential trash.