Ben Franklin Transit has replaced the floors on six buses because of mold.
The fixed-route buses were among the 24 the transit agency bought from Sound Transit in Seattle for $1 each, said Ben Franklin Transit spokeswoman Christy Watts.
Ben Franklin employees tested each bus for mold, and six came back positive, she said.
"The maintenance department went through every single one of them and tested them and did everything they could to bring them up to speed," she told the Herald.
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The repairs were made after a driver noticed the mold, Watts said. Each bus cost about $1,000 to fix and all are back on the road.
"Even though we had to spend $6,000, it was still a heck of a deal," she said.
Watts said no one was sickened by the mold, but a Ben Franklin Transit driver said several employees had allergy and sinus problems. The driver, who asked that his name not be used for fear of losing his job, said passengers also could be at risk.
"I worry about some of the public we transport," he said. "They are in many cases in fragile health. They are being exposed to that stuff, and they don't know it."
At one point, the driver said the buses had mold growing out of the seats.
Ben Franklin Transit bought 11 buses from Sound Transit in 2011 and 13 more in 2012, Watts said.
Buses delivered in January 2012 replaced 20-year-old buses with more than a million miles on them, according to Herald archives. The 1999 Gillig buses were used on Seattle-area freeways, meaning they didn't have as much wear and tear as some buses driven within the city.
The buses have features like wheelchair lifts, brake retarders and anti-lock brake systems, which the buses they replaced didn't have. They also produce lower emissions than the older buses, have reclining seats, foot rests and overhead storage.