I'm about to put in 4 (4"x6" pressure treated wood) pylons, through the ice. upon which I intend to build a 32' long bridge which will span a 30' wide canal. The canal connects two ponds and is about 7' deep in the center. (i.e. the canal side slopes are sort of steep.) The pylons are to be located about 1/3 the distance from the shore, 2 from each side, where I estimate the water depth to be about 3'. The pond bottom soil is yellow clay and then blue clay.
My question is how deep in the clay should the stanchions (pylons) be so that the ice will not lift them up in the winter? I'm in southern Michigan where the winter ice can get to 8"-10" thick. Any other thoughts on this subject are also welcome. Anyone have any experience with such a construction subject to seasonal ice.
If it makes any difference: I'm not sure how much the wood bridge will weigh but my guess is several hundred pounds due to length and 6' width; basically a wood deck sort of construction.
