Snakes in septic tank

Question
We had to redo our septic tank....i live on a farm and as they were taking out the old drainfield for our septic tank a nest of garter snakes fell into the septic tank.  Is it possible for them to survive, if so how long? Will they be able to crawl into my house and out a drain.  I am deathly afraid of snakes, is there any way to kill them and keep them from coming in through my pipes?

Answer
Highly doubtful though probably not impossible for them to find the way out.  The best thing to do (or would have been anyway) would have been to get them out of the tank BEFORE you covered it up...  I don't participate in the killing of snakes, especially harmless ones like garter snakes-seems kinda ridiculous to me.  The toxic fumes and horrible conditions in the tank will probably accomplish your goal of killing the snakes.