Merging Multiple Vertices I am wondering if there is any tool or way to kind of Weld (merge) multiple vertices at once, 



AltM > Merge at Center doesn't do the job.



Doing by one takes a lot of time so it's inefficient way of going about it.
Use the Bridge tool from the Loop Tools addon to connect the loops, then slide them into each other and remove doubles. You can also cut a new loop between them to get the exact midpoint.