Initial excavation for gravel road build... how deep?

[Dadnatron]

I have built a gravel road on my property, along a mild slope, and everything went well. However, I now need to put in another road, about 300yds, which 'Ts' off the first, but runs primarily along the bottom of the slope. The depth of topsoil along the new road is roughly 3ft.

For the initial road, I cut the hill to firm clay, and all in all, I think I overdid it by far. I think the road will be extremely stable, however, the guy who originally gave me a quote for the road said I over cut it and could have done much less and still had a good road. (He is no longer in the area to ask this question.)

So my question is... how much of the topsoil do I need to remove? I cannot realistically pull 3ft of topsoil from a 14' wide trench only to fill it with clay then gravel on top. The road is essentially flat, will have a culvert on both ends for 2 small waterways, and has a little curve. I absolutely want to use a good Geotextile, and will use it regardless of how much I remove. But I'd like to remove as 'little' as possible to get the realistic benefits I will need. It will have trucks on it for a barn build at the other end, then just a single family farm traffic from that point on. Nothing heavier than a F350 pulling a horse trailer, in all likelihood, and that rarely. Tractor, pickup, and cars for the most part 99% of the time.

 

[rustyshakelford]

Cut it down 4” so you can roll your tile and bring in that much gravel. Give it a slight crown so water will run off it. Actually cut it down 2” then build up 2”above grade

Brett

 

[RNeumann]

With road fabric (geotextile) 6”+ is probably all that is needed for a residential drive. As recommended rolling the soil before the fabric will also give you a good indication of who stable things are.
Understand you are already doing more than 90% of folks would do....

 

[4570Man]

I don’t have to cut down more than a few inches to get through the top soil. Bedrock is a foot or less in plenty of places. Trying to get a septic tank in without adding fill on top is nearly a joke. Count yourself lucky on this deal.

 

[Gary Fowler]

You only need to excavate deep enough to remove the organic matter (roots, grass etc.) then put down your geotextile and build up from there.

 

[oosik]

4570Man - - did you somehow slip in on the back side of my 80. I have large areas of exposed basaltic lava bedrock and some areas actually have four feet of soil over bedrock.

Other than the best view in the world - my current house location has access to sufficient soils to allow installation of a drain field.

Most all my areas where scab rock is exposed still have exposed ash from 1980 Mt St Helens. Such a pleasure when the wind blows.

The majority of my mile long driveway is built up from a solid basaltic lava base.

This area is not called the Scab Rock Lands for no reason at all.

 

[Tractor Seabee]

Your intended use does not warrant removing all the top soil as others have implied. Just remember over time you will have minor settlement issue (probably not evenly) as the organics in the top soil breakdown and compress. I would excavate enough to putting a 6" layer of compacted 4" crushed rock with a 4" layer of 1 1/2" minus topping compacted to 90-95%. The 4" will help bridge over isolated areas of settlement. It may then last a lifetime with minimal maintenance. That minus gravel has a lot of small stuff and crusher fines that compacts extremely hard and dense.

Ron

 

[Oldoak]

Your intended use does not warrant removing all the top soil as others have implied. Just remember over time you will have minor settlement issue (probably not evenly) as the organics in the top soil breakdown and compress. I would excavate enough to putting a 6" layer of compacted 4" crushed rock with a 4" layer of 1 1/2" minus topping compacted to 90-95%. The 4" will help bridge over isolated areas of settlement. It may then last a lifetime with minimal maintenance. That minus gravel has a lot of small stuff and crusher fines that compacts extremely hard and dense.

Ron

:thumbsup:

The only thing that I would do different is go about 8" thick with the 4" aggregate.

 

[Dadnatron]

After putting down fabric, on my initial road! I put down #2s, then topped with CSB (crushed stone base 1 1/2” with 25% fines. I planned on adding DGA however thus far, it has compacted well with just traffic and formed a solid topcoat.

Given this will be on a softer base, I assume you mean I should ‘roll it’ (base under fabric) via sheeps foot compactor. After adding 4” of #2s, how do I compact it? That seems like a relatively thin lift and I’m not sure the best way to compact it before adding 4” CSB. And then to compact that.

 

[Lelandwelds]

Three foot of soil? You won the dirt lottery!

My place is rocky enough for a passable road in some places without any additions. I have never used the geotextile. I use a 3/4" and under crushed rock with lots of stone dust. I wish I needed all the prep you are considering.