Honolulu's only municipal landfill is filling up faster than anticipated, forcing the private company that runs the operation for the city to request permission to raise the height of portions of the landfill by about 40 feet, state officials said.

The Health Department's solid waste chief, Steven Chang, said the city and Waste Management Inc. last week requested a permit modification for the Waimanalo Gulch landfill, noting that the part of the landfill that takes ash from the city's HPOWER garbage-to-energy plant is expected to reach the permitted capacity by next month.

Chang said the request would take the height to 275 feet in some segments of the ash landfill. Currently, it ranges in height from 100 feet to about 235 feet, he said.

Waste Management Inc. spokesman Eric Rose said in a written response that the permit modification process requires a public hearing and administrative review of the application, which is expected to take three to six months. He said no new construction is required to allow for the new height and additional ash.

He said the application for a grading modification would provide additional capacity needed until the permit's scheduled end in 2008.

Honolulu Mayor Mufi Hannemann already has said that the city may have to seek an extension beyond that deadline without another landfill or waste disposal alternative. Wai'anae residents have long complained about the smell, litter and associated problems of having a landfill in their backyard and have vehemently opposed any extension.

Last week, the state Health Department fined the city and Waste Management $2.8 million and cited them for 18 types of environmental violations.

Chang said many of those violations have been corrected, but he said overfilling of both the ash and the municipal solid waste sections of the dump remains a problem.

He said the permit extension appears to be an attempt to get permission for some of the overfilling that has occurred.

But the company also has put in improvements and berms to help shore up the stability of the landfill, Chang said, which it is citing in its request to go higher.

As the permit modification is being considered, state health officials would evaluate any ongoing or new violation or fine, Chang said, but there are few options for the city in the short term.

"They have to continue to operate or we won't have any place to take our trash," he said.

Reach Robbie Dingeman at rdingeman@honoluluadvertiser.com.