The dam feeding Lake Nokomis (Rice Reservoir) is the Willow Reservoir Dam, which is upstream from Nokomis. The dam that creates the Rice Rersvoir is the Bradley Dam. Which are you referring to?
If it is the Willow Dam, it would most likely have negligible impact on Lake Nokomis. However, if it is the Bradley Dam, I would guess that lake levels could potentially be lowered dramatically to work on the dam. I guess it depends how extensive the "rebuilding" is.