wedling,
The welding of mis-located holes, as described in C-5.26.5, looks to be appropriate for your situation. As HgTX has mentioned, this is part of the commentary and a mandatory part of AWS D1.1. Although it is helpful. It is common for fabricators to fill mis-located hole by the method mentioned by HgTX, to "insert rod and swirl it around". To weld in a spiral from the outside of the hole to center layer after layer until filled. This will present difficulties if the weld is required to have any type of volumetric NDT (RT or UT). If I were in your situation I would utilize the advise in the commentary. Use a similar material cut to the Dia. of the hole as backing. Shape the hole into a canoe shape on the other side, to allow for the deposition of stringers. Weld it out, and grind flush. Next back-gouge the Backing material to clean weld metal ( I would also suggest a MT examination at this point, if final weld requires NDT ), shape the gouged area to a canoe shape as was done on the other side. Weld it out, grind flush. Perform volumetric NDT if needed. Now drill hole in correct location.