Trees Torch News Today : Breaking News, Live Updates & Top Stories | Vimarsana

And potentially trap firefighters. >> we had up to 43,000, that creates its own weather. >> reporter: firefighters are also struggling to protect this huge reservoir which supplies 85% of san francisco's water and is being slowly polluted by falling ash. the challenges are enormous. the fire is being spread by what is known as crowning where the tops of trees torch, spreading faster than on the ground. >> you ever get worried any of the trees will come down while you are in there working? >> that's why we train the way we do. keep our heads up. >> reporter: more than 3,500 firefighters are in ...

>> we had up to 43,000, that creates its own weather. >> reporter: firefighters are also struggling to protect this huge reservoir which supplies 85% of san francisco's water and is being slowly polluted by falling ash. the challenges are enormous. the fire is being spread by what is known as crowning where the tops of trees torch, spreading faster than on the ground. >> you ever get worried any of the trees will come down while you are in there working? >> that's why we train the way we do. keep our eyes up. >> reporter: more than 3,500 firefighters are in this battle staged along three flank...