A 32-acre grass fire ignited just west of the Nicasio Reservoir last Wednesday when a mower operated by a county road crew struck an object, causing a spark. Marin County Fire Battalion Chief Bret McTigue said road crews always carry water for such instances, but due to the critically dry fuels, the blaze exploded before they could douse it. He advised residents to mow grass before 10 a.m. David Briggs