NORTH MANATEE -- Ground water containing ammonia levels 15 times higher than normal leaked from the abandoned phosphate mine at Piney Point onto a nearby farm in December and January.

Florida Department of Environmental Protection officials say the polluted area, some 300 feet from the mine, was limited to a Florida Power & Light easement on the farm and that no harm was done to crops.

But the seepage is another black mark against the mine that has had pollution problems since owner Mulberry Corp. went bust, leaving the DEP to clean up the mess.

"There is no excuse for any kind of a spillage coming from the Piney Point site," said Glenn Compton, director of ManaSota-88, a local environmental group. "This is an indication that the DEP could be doing a better job of managing the stack."

The DEP has spent more than $80 million cleaning up Piney Point. It is expected to cost an additional $40 million.

The polluted farmland was discovered in February. It was caused by debris from the cleanup operation falling into a seepage ditch that was built to keep runoff and polluted ground water from the mine away from farms to the south.

The ditch works by making ground water flow toward the mine. But the rise in the water level caused ground water laden with ammonia and nitrogen to seep toward the farm.

John Coates, program administrator for the DEP's Bureau of Mine Reclamation, said the DEP would continue to monitor numerous wells around the mine. Debris from the ditch has been removed and work is being done to cover ditches to prevent a repeat of the problem.

"I'm pleased with how quickly folks responded and were able to detect there was an issue there and were able to correct it," Coates said. "Fortunately, we never had to face any farming issues."