***THE CACHE IS NOT AT THE POSTED COORDINATES***
At the posted coordinates you will find a signpost that has some distance markers on it - One to the Greenbelt Route and the other to the Great Lakes Waterfront Trail. Add both of these numbers together then divide the total by 1,000. Add this final number to these fictional coordinates:
N 43° 40.005 W 079° 39.767
You can validate your puzzle solution with certitude.