Got word that my road through a type 7 wooded swamp is getting permitted (silvicultural exemption), so now the decision on how to build it needs to be made.
I had the DNR TEP guy out last fall and he did some bore samples which discovered 3" of clay over sand under 4' of peat muck. So it's shallow enough I can skip geotextile, but I question the value of that savings? If I use fabric, it'll add about $450 per layer on the cost, where my other materials will be around $2500 or so (16x250' road bed).
I also question the "best practices" guidelines which state to put the fabric down over the organic material, and then put fill over it. Seems like a "skim coat" of large stones would make a better base for the fabric, even if some of that ended up sinking.
Another benefit to a base layer under the first coarse of fabric would be the ability to anchor the culverts with the fabric. The culvert my swamp drains to has heaved over the past 5 years or so and is coming up through the asphalt. I'd like to prevent that on mine!
So right now I'm thinking: muck/4-6" riprap to level it out over the stumps and slash/geotextile/gravel/then class 5 with fines for the surface.
I can also do corduroy and float it, but I think that'd work better if the ground was cleared. Maybe do corduroy over the fabric and below the gravel?
The swamp will start thawing when the temps reach the 40's and that could be this weekend.
Any input is welcome! I didn't think I'd get permission, or I would've done more site prep last fall.