3ds Max :: Splines - Vertices Won't Weld

I have recently decided to restart on an older project, made in some older software long ago, a somewhat simple racetrack.

I decided to load this model into 3DS, and modify it to add several alterations and some heavy modifications. In order to retain it's original shape. I had decided to convert it to a Spline. According to my plans, this was the best solution, apparently.

And that's where the issue settles in. Due to the fact that the model was triangulated, when I selected the "Select Edges" and "Convert to editable Spline", the model became a skeleton of it's former self, and when you delete the un needed vertices the remaining spline consists of many un connected points, thus making Path deform and Sweeping impossible.

I cannot weld the vertices together, every attempt made thus far had been un productive, the vertices remain un connected and un usable.The spline in question can be viewed in the attachment.