By Maria St. louis-sanchez maria.sanchez@gazette.com -Crews continue to clean up ammonium sulfate that spilled after a BNSF train derailed Sunday night near downtown Colorado Springs. Joe Sloan, a railroad spokesman, said crews finished cleaning up the chemical that was spilled on the ground after 10 cars derailed. Ammonium sulfate is an innocuous material commonly used in fertilizer.On Wednesday, crews were continuing to remove the material that was left in the cars that had turned over.