Probaby buried deep underground in concrete bunkers. As I understand it, you must neutralize biological/chemical weapons with extreme heat. Can't just blow them up the normal way because that would be the same as releasing them.
An imminent thread calls for an imminent destruction.
Do we know where in Syria where this weapons are? If not nuke the entire ME.
Time is up. This would dovetail well with the same message to Iran and perhaps force them to see the light. It should be an air campaign from 40,000 feet with unimaginable bombings. Killing hundreds of thousands may save millions.