The area with the huge reservoir? Good luck, that could be a big survey if no records of original corners exist. Hopefully some of the lands were surveyed when they built the dam.
Use the field notes from the GLO surveyors. I briefly looked at them this morning, and it looks like they set all section corners and quarter corners. If you have to resort to a full retracement survey, I recommend that you consider using it for finding or restoring the corners in the same place that GLO set them. Under normal circumstances, I would also recommend at least initially considering that the pro-rating would come from the proportionate distances GLO recorded on the survey if you have to go to the very last resort of pro-rating which is often dangerous, and in that case might also recommend boundary agreement. I would not normally find a pro-rating or closing corner instruction more reliable than simply trying to follow what the GLO did and last resort pro-rating using the GLO's numbers.
That is an old survey in some tough terrain and where much appears to be disturbed. Boundary agreement might be highly recommended in case someone decides to build the Mariott Hotel one inch from the section line next to the water a couple years down the road.
It looks like Section 4 may be subdivided: