Firefighters wearing safety masks slogged between smoldering mounds of mulch Friday, spraying a special chemical foam city leaders hope will finally smother a massive fire.

Smoke has been drifting from the Durham Yard Waste Compost Facility into nearby neighborhoods for 13 days. In a media release, the city said the foam is the same product used to douse debris at the World Trade Center in 2001. City Manager Patrick Baker has said the fire will be out by Oct. 2, if not sooner.

As a giant mechanical claw grabbed wads of burning wood and leaves Friday, firefighters sprayed the mass with the soapy foam, which was mixed in 3,000-gallon batches and pumped through hoses. Clouds of steam erupted from wherever the foam was directed.

Firefighters and a contractor hired by the city ferried a steady line of tanker trucks filled with water to the dump because there is no fire hydrant nearby. Small streams of the foam flowed off the burning pile and into a nearby ditch. The stuff is fully biodegradable, officials said.

"Thus far, the suppressing agent appears to be helping us make more progress in cooling down the debris that had been smoldering and being able to spread it out," said Durham Fire Chief Bruce Pagan in the statement. "The smoke also is diminishing, especially in the areas that have been doused with the suppressant where steam is being generated, which means it is cooling down. Citizens should notice a reduction of smoke."

A separate crew of workers were busy loading a huge pile of wooden shipping pallets into a machine that ground them down to mulch. The pallets had been stored at the center illegally, according to state officials, and the city must remove them to get its operating permit renewed. The state has threatened to fine the city up to $5,000 a day while it is in violation.

It was estimated Friday it will cost about $117,000 to put out the fire and clean up the mess at the dump, which had been operating without a required state permit for more than two years before the fire broke out Sept. 10. Durham won state approval for a 60-day operating plan the city hopes will lead to the renewal of its permit, but in the meantime it will no longer dump yard waste at the site.

The city also said Friday it will pay to relocate some nearby residents suffering health problems from the smoke. The city will consider covering "reasonable housing costs on a case-by-case basis" for people living along Glenn Road and in the Crowne Pointe and Glenstone subdivisions.

"We want to assure the public, especially those citizens living near the yard waste site, that we are doing everything that we reasonably and safely can to put the fire out and diminish the smoke as soon as possible," Baker said in the statement. "While we have advised residents affected by the smoke to remain inside, certainly if they have health concerns or have existing health problems, they should consult with their physician and leave their homes if necessary."