Firefighters from Arlington and Alexandria spent nine hours yesterday dousing and cleaning up hundreds of tons of trash after a fire broke out in a 30-foot-high pile of refuse at the Arlington County Waste Transfer Station.

The 8 a.m. fire at the facility at 500 S. 31st St. started by spontaneous combustion, said Arlington Fire Department spokesman Stevan Hynson. There were no injuries, although some firefighters suffered mild heat exhaustion.

Because of equipment failure and trash brought from Alexandria, hundreds of tons of trash had accumulated at the facility, said Arlington Director of Public Works Henry S. Hulme Jr. Heavy, packed trash can spontaneously ignite from heat generated in the pile, fire officials said.

The station, which is scheduled to close in October, normally transports about 500 tons of commercial and household refuse a day, Hulme said.

Three of the eight tractor-trailer trucks that are operated 16 hours a day hauling the trash to a Lorton landfill broke down last week, said Hulme. In addition, Alexandria brought in about 400 tons a day for three days this week and last when its facility was closed for repairs, he said.

Hulme said workers are usually able to clear all but 50 to 100 tons of trash each day. "We got behind with Alexandria's {trash} and we just never caught up," he said.

The volume of the 30-foot-high, 150-foot-wide mound of paper, twisted metal and discarded mattresses, made it difficult for firefighters to put out the blaze, said Hynson.

James Gilbert, the load operator who spotted the fire in the warehouse-type structure, said he saw smoke and flames grow higher than the pile.

Five Arlington firefighting vehicles and three from Alexandria were called to the scene and 50 firefighters assisted in the operation.

It took firefighters about three hours to put out the blaze and at least six hours to move tons of trash out of the facility and wet it so it could be hauled to a nearby compactor, said Hynson. There was no damage to the structure.

A $75.9 million trash incinerator, the Ogden Martin Systems of Alexandria-Arlington Inc., at 5301 Eisenhower Ave., is expected to be in operation in September. The plant is designed to convert trash into energy, and will be used by Arlington and Alexandria.