Foothills threatened as Bobcat Fire swells. Santa Ana winds lead to San Gabriel Valley evacuation warnings. The fire started on Sunday, September 6 near the Cogswell Dam and West Fork Day Use area. It had grown to 10,344 acres with no containment by Tuesday evening. It is moving slowly toward the residential areas of Monrovia, Arcadia, or Duarte, but an evacuation warning has been issued for Arcadia.