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IOWA CITY – The size and type of the fire at the Iowa City landfill make it especially difficult to deal with, according to a landfill fire expert.

At 7.5 acres, the fire would be considered large, said Tony Sperling of Landfill Fire Control Inc. His Vancouver, Canada-based company specializes in helping landfill owners put out and prevent fires.

Another complication, he said, is that what is burning is the landfill lining, which is made up of shredded tires. That means it's essentially a tire fire, he said, which are notoriously difficult to extinguish.

“You have a real problem with that,” Sperling said.

The fire started at the city-owned landfill, located just west of town, on Saturday night. The city at this time is planning to let the fire burn itself out, saying thatâ??s the safest and most cost-efficient thing to do.

The media was allowed to tour the landfill on Tuesday. The fire has been contained primarily to an unused cell, which was burnt black and had small patches of fire scattered about. The flames were roughly 6 inches high.

Smoke was low to the ground and almost seemed to crawl out of the 160-acre landfill.

The fire measured at 1,200 degrees in some places, said Geoff Fruin, assistant to the city manager.

A cause has not been determined, but Public Works Director Rick Fosse said it most likely was something hot being brought in with a load during the day Saturday that was dumped on the edge of the active portion of the landfill. That could include something like charcoal from grilling or debris from a burn barrel, which some rural residents use to burn trash, he said.

Sperling and Jeremy O'Brien, director of applied research at the Solid Waste Association of North America, said so-called “hot loads” are the most common causes of fires in active landfills.

There are about 8,400 dump or landfill fires annually in the U.S., according a 2002 Federal Emergency Management Agency report. It was not immediately clear Tuesday if more recent numbers were available, but Sperling, who helped with that report, has said FEMA data showed there were 3,108 such fires in 2010.

Sperling, whom O'Brien called the “guru” of North American landfill fires, said most U.S. and Canadian landfills have a couple of minor fires each year that are put out within a few minutes.

By his count, there have been about 20 major landfill fires in the past decade. His company uses a numerical scale to rate fires, with level four being the biggest and reserved for those that take more two weeks to extinguish.

Iowa City is letting its fire burn out, a process city officials estimate will take more than week. Given that and the size, Sperling said it could rate a three or four on his scale.

The fire is primarily confined to an unused cell built a year ago, according to the city. It is burning a liner system made up of shredded tires, which is producing a plume of black smoke.

“That's a real shame. Those linings are expensive and are there to protect the environment,” O'Brien said.

The city has set a preliminary damage estimate of $4 million to $6 million. The city is pursuing insurance claims and looking at other financial resources, including available funds and borrowing money, to pay for the cost, City Manager Tom Markus said. State and federal assistance also may be a possibility, Finance Director Kevin O'Malley said.

“It's a disaster to any degree,” Markus said.

The landfill cell cost $7.8 million to construct, he said. The lining is ruined, Fosse said, but the same area should be able to be used for a new cell, he said.

There is about a year's capacity in the landfill cells that were not affected by the fire, Markus said

Tires that catch fire break down into hazardous compounds, including gases, heavy metals and oil, according to the U.S. Environmental Protection Agency.

Fosse said city officials are not concerned about leakage because there is a four-foot layer of compacted clay under the cell and a drainage system that collects runoff.

Public health officials have been taking samples and say air quality is not a concern at this time. People with lung and heart conditions or who are pregnant, older or have young children at home are advised to stay away from the smoke plume.

In the first couple of days after the fire started, the plume was moving north over scarcely populated areas. With a change in wind direction Tuesday, it shifted east, toward Iowa City.

The dark smoke was especially conspicuous in the nearly cloudless blue sky.

The Gazette's Hayley Bruce contributed to this report