Novice looking for advices

Hi experts!

i’m trying to make a pipe radius of 2.5mm aroung this surface.


But i faced an issue where as there is a gap between the design and the Subd-pipe.

I’m wondering if there is a way to close up that gap without cutting the main body of the design.
Here’s a similar copy of the model, i can’t show the actual as it is a part of my major project.
Model.3dm (2.1 MB)

Any advice would be welcomed, Thanks