-Two areas used in Davis' DNR mussel survey (1994) IC and ID were selected because of their proximity to the Northfield Dam.
-Sites for sampling within each of these two areas were determined using a random number generator prepared with Pascal computer programming.
- Survey sites were classified by their distance from the dam, as well as their distance from the shore.
-The sites' proximity to either bank were designated qualitatively:
right, middle or left part of the river (facing downstream).