reducing project size - final cut pro x

Hello I'm working on a final cut pro x project that is going to be between 10-15minutes in length. This is the 6th project I've worked on and the previous have been between 50-150gb. The problematic project has grown to 692GB. The problem is that it is on my startup hard disk and I don't have space for it on my external drives either.

I think there must be a problem because this project is so large. Does anyone have some suggestions for how I reduce the size of this project or find out why it is 5 times as large as other projects of similar length and footage.