I would rent a back hoe and dig around the pipe as much as possible to get as much drainage to the pipe.
If you don't plan to keep the pipe as is...then cut it off at the lowest point after the "trench" digging near the pipe...
My experience is to put in a new pipe and disable the old...
Draw the water in and let it flow..
Dry the rest out and go to work while you have a small pond around the pipe...
Just some late night random thoughts..
Good luck.
