The company that operates the city's only municipal landfill yesterday said it is stunned by the size of a $424,000 fine imposed by the state and plans to appeal.

"We are shocked by the size of the penalty that (the Department of Health) is seeking," Joe Whelan, district manager for Waste Management of Hawaii, said in a statement. "We will appeal these alleged findings and believe that the excessive administrative penalty is wholly disproportionate to the alleged violation."

It was the second time in five years that the city and Waste Management have been fined over operations at Waimānalo Gulch Sanitary Landfill near Nānākuli.

The Health Department on Thursday said the city and Waste Management were being fined for failing to follow specifications in building a berm that helps support the western wall of the landfill.

The department also cited the city and Waste Management for not reporting the deviation from the plan, and for failing to provide quality assurance reports in a timely manner.

Steven Chang, chief of the Health Department's Solid and Hazardous Waste Branch, said health officials did not find out about the violation until they read reports Waste Management submitted in February, nearly three years after the berm was constructed.

Whelan said the berm is larger than specified in the plan the company gave to the Health Department "because of the space restrictions at the site and significant limitations on where excavated dirt and rock could be placed."

He also noted that Chang stressed the violation did not result in a safety issue.

"We are very confident that the landfill is safe and stable," Whelan said. "The protection of human health and the environment is always our first priority at Waste Management."

The company's statement did not address why it had not told the Health Department about the plan deviation, or why it failed to provide quality assurance reports in a timely manner.

Kit Cole, a Waste Management spokeswoman, said the company will pay the entire fine.

"We're the operator of the facility and, in this case, we feel that's appropriate," Cole said.

City spokesman Bill Brennan last night referred requests for comment to Waste Management. On Thursday, the city said it couldn't comment because it had not yet seen the actual violation notice.

In 2006, the city and Waste Management were slapped with a nearly $2.8 million fine for exceeding waste height limits, allowing excessive liquid buildup or leaching, and failing to cover the solid waste daily.

Health officials at the time said the fine was the largest ever levied against a landfill operation in Hawai'i.

West O'ahu residents have complained for years that the landfill should be shut down because it is a nuisance and a visual blight. Opponents also point out that former Mayor Jeremy Harris promised in 2003 that it would close by 2008.

The landfill's last permit ran through Nov. 1, 2009. But the state Land Use Commission voted last August to grant an extension and expansion plan. That approval requires the city to close the landfill to all materials except ash and ash residue by July 1, 2012, far less time than what was being sought by the city Department of Environmental Services.

The city, which wants a 15-year extension, has appealed the decision to state Circuit Court.

Meanwhile, the Health Department will hold a public hearing Monday night in Kapolei Hale on a request by the city for an administrative permit to expand the facility.