Stabilizing culvert over muck?

[Jim Timber]

I'm in the process of getting final approval for a road through a wooded swamp (should have my last signature Friday). The base is about 4' of muck over 3" clay with sand under the clay. Rather than guaranteeing I need 4' of fill brought in, and risking peeling out the clay and draining the swamp, I've decided to float it with a base of riprap over the root mat, and will be putting corduroy over the riprap and then gravel over the corduroy, with a final drive surface over the gravel after a period of time to ensure there are no drainage issues or uneven settling that need to be corrected. I have pretty much free reign on the design, as it's a private road.

There's a spring seep that feeds the swamp somewhere on the property (the swamp is roughly 6 acres with me and a neighbor owning equal halves), but it doesn't flow much (maybe 2" of the bottom of a 18" culvert when there's consistent rain) - of course my road bisects it's path, so I need some culverts to manage the water.

I'm going to go with the biggest double walled poly pipe I can get locally, and multiply them as needed to get the volume I think is sufficient. The 18" culvert that drains this area into the lake isn't big enough and has over run the town's road several times in recent years with heavy rains. I'd like 24" as a minimum, 36" would be even better but I don't know that I can find it without trucking it in (which I haven't ruled out either).

With the muck and clay, how would you guys suggest building up and firming the base to place the pipes? I've got a Caterpillar outfit 6 miles from me, so I plan on renting a mini excavator to dig and tamp the holes. I can bring gravel in, or sand. I just don't have the experience with this stuff to know what the better option is.

 

[Egon]

Dig out the culvert bed to the clay and backfill with crushed rock just as tour have planned.

 

[vtsnowedin]

Dig out the culvert bed to the clay and backfill with crushed rock just as tour have planned.

+1 on that.
I'd do the whole road with shot rock pushed in to displace the muck full depth and dispense with the corduroy. A skill bulldozer operator will have the loads dumped on the already finished fill and push the load down and ahead pushing the mud wave in front and not trapping any muck under the rock. Bring the ledge fill to a foot above the water line and then cap with a foot of gravel.

 

[Jim Timber]

There's no dozer involved in this one though. I'm doing it with my tractor and a rental mini-ex.

The length of the swamp being filled is 250 feet, so it's not a huge project. So far the tractor's doing the job quite well.

The tree leaning hard to the left has been taken down and is just about at the high ground on the other side.

I got 93 feet over frozen ground and still have a few yards that aren't spread thin enough with 5 (12yd) dump truck loads. I figure with the soggy ground I'll be looking at 10 more to get across with a fordable layer of rock down after it starts sinking in.

This was after the 5th load was dumped.

The street leading in has a 7T axle limit, which prevents me from using bigger delivery trucks.

 

[vtsnowedin]

Well a mini exc can dig a hole down to the clay and the tractor can push rock in to fill up to grade then move the mini exc ahead and repeat. It is important to not overlay some of the muck as it will pump up through what ever you lay over it and contaminate it to the point that it is just bony muck. I've used a tractor as a substitute for a bulldozer quite a bit but it is hard on them and takes a lot more time not having sufficient weight pushing the material around.

 

[Jim Timber]

Boney muck with the root mat should be sufficient to hold the weight of the tractor while laying the corduroy. I don't think I want to fill this to the extent needed for a solid base down to the clay. Semi traffic will be limited to building materials, my machinery, and steel for my manufacturing business. The primary loads this road will see are automotive traffic. Corduroy is also a the BMP for roads through this wetland type according to our DNR and the ACoE, and I have plenty of trees to use on site.

I forgot to mention I have 8' wide chain link fence to lay down before the logs go down. I'll put two strips of that over the rock instead of geotextile because the road's shoulder isn't firm enough to anchor fabric as the manufacturers suggest needs to be done for it to work right.

 

[vtsnowedin]

Ok your doing things to please a DNR and their best management practices. Your not talking about building a durable road. Forget all my previous posts.

 

[Jim Timber]

Sorry, I don't have a governmental body to pay for 740 yards of fill for this project.

 

[vtsnowedin]

Sorry, I don't have a governmental body to pay for 740 yards of fill for this project.

You think your corduroy is going to cost you less then 740 yards of fill?

 

[Jim Timber]

Yes, because I can cut it off my property. How do you think a course of logs would cost $11,000?