Unfortunately I'm not sure that there's any way to make any repair to that pipe without lowering the water level to that point, hopefully its not too far down.
It should be either 4 or 6" PVC, I'm not aware of any 5" ever made.
Another option may be to permanently cap it off on the backside of the dam and install a siphon overflow system to carry your excess flow to exit the pond.
Good Luck, let us know how it goes.
I personally don't know any contractors in Virginia, but I belong to a National Association of Land Improvement Contractors with individual chapters in most states in the eastern 2/3rds of the US.
Your Virginia Executive director is Kim Johnson, and her email is
[email protected], she should be able to hook you up with a local, reputable contractor in your area. Or you can google their site.
Hopefully I am allowed to give you that information on this forum, if not I apologize and will delete this comment.