democratandchronicle.com — One of the most remarkable environmental messes in local history was triggered 41 years ago when a train derailment dumped 200 tons of toxic chemicals on the porous bedrock of rural Genesee County. RocDocs database: Interactive map of area affected by toxic plume It was the single largest spill on record in New York state of the human carcinogen known as trichloroethene, or TCE.