Jason you forgot to include the height of the park above lake level... in your haste to be right, you didn't think of that.
From google. "Warren Dunes State Park. Warren Dunes has three miles of shoreline, six miles of hiking trails and is open year-round. It also has a dune formation that rises 260 feet above the lake with spectacular views and 1,952 acres of recreational opportunity."
So you are not 6' in elevation, you are 266' of elevation.. now let's calculate.
https://dizzib.github.io/earth/curve...&unit=imperial