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  1. #1
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    Topsoil into Clay?

    So, I've found post all over the internet about turning clay into top-soil (for gardening purposes), but I'm having the complete opposite problem. Most of my local trail area is primarily topsoil (unless you dig down a good foot and a half), and I was wondering if you guys have any tips on firming up top-soil that it's more shapeable, and well you know.... good for building

  2. #2
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    We have topsoil with loose and embedded rocks on clay on rock. The clay actually makes a great base to cut into for berms and allows the riding line to be on a solid base with a limited depth of soil above that completes the berm. Sometines we use inslope drains with or without rock. If you have clay under topsoil that may work for you. However, water can move above the clay layer and you have to think out positions for cross drainage at times.

    If your lower layer is all rock, then you need to build with soil and add water as you go. Small amounts of wet, topped with dry soil, tamped down and repeat and repeat and repeat.

  3. #3
    Almost Human
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    Quote Originally Posted by arkon11 View Post
    So, I've found post all over the internet about turning clay into top-soil (for gardening purposes), but I'm having the complete opposite problem. Most of my local trail area is primarily topsoil (unless you dig down a good foot and a half), and I was wondering if you guys have any tips on firming up top-soil that it's more shapeable, and well you know.... good for building
    Soil is classified based on 3 types of solids, sand, silt and clay.

    Top-soil doesn't tell anyone too much about what it is.

    I would suggest doing a soil texture test on the top-soil to see what the percentages of sand:silt:clay are and then start looking at soil modification.
    DIY Soil Texture Test for Your Yard | Danny Lipford
    (just google "determine soil texture" and there are several pages that show you how to do this)

    After you get your results determine what type of soil you have using the texture pyramid.


    Clay is sticky. Silt is slippery. And sand is coarse and will not stick together. Judging by your post I would guess you have a sandy loam.

    Other than bringing in some clay and amending the soil (really hard work) there's probably not a lot you can do.

    There's some stuff called Gorilla Snot you might try. Albeit it washes off after a period of time. They use similar products on BMX tracks.
    Gorilla-Snot® Soil Stabilization & Dust Control from Soilworks®

  4. #4
    Cutlery Fiend
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    So then what is the best type for building trail treadway?

  5. #5
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    IMBA says loamy soil. It's a mix of all 3 types. It compacts well and drains well.

    If you are building berms and jumps (i.e. pump track), you want a bit more clay in the mix for a durable smooth hard surface (when dry). Not sure the exact ratio for that application. I'm sure someone can jump in with the correct numbers.

  6. #6
    saddlemeat
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    70-80% sand 20-30% clay is your basic adobe mix.
    A Useful Bear is a handy thing.

  7. #7
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    If it is not possible to use imported materials to strengthen soil, try this. Armour the base, then add whatever soil you have with lots of water. Make it deep enough to push stones up to 15cm X into the wet soil and then cover with more soil. Keep adding stone (push in by foot and then ram home with the end of a trail rake, mattock etc and then add more soil. it takes a while, but the tread can be stabilized even if clay is not available. Finishing with embedded small stones/pebbles makes the tread faster and encourages even wear. Just don't add stones with dirt - one or the other at a time when there is enough water available.

  8. #8
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    We used to add lime (calcium oxide) to sandy, loamy soil which would help it harden and compact. Works great for small areas (tennis court size, etc.) but might be a little too much for a long trail. You can always do an experiment.

  9. #9
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    I've though about it a bit and I suspect what the OP meant by top soil is the top layer of soil with a high percentage of organic material -- dead and decaying plants and such. It's not good as a trail surface as it retains moisture and quickly turns into muddy snot that takes forever to dry up. I don't know how you turn that into something useful.

    You need to dig down past that layer to find good soil for your trail bed. If you are on a flat surface, that's not practical, because you just end up digging a water-collecting trench. This is one of the reasons why IMBA recommends bench cut on sloping terrain. If done correctly, you dig down past the organic layer to find good non-organic soil to build your trail on, broadcast the excavated organic layer downhill, and if everything is done right, rain water will sheet down the hill and across the trail and not collect on the trail.

    Sometimes you don't have much sloping terrain to work with and everywhere you look is flat. If that's the case, you need to work the micro variations in the terrain. Route your trail across every slight bump and high point you can find. When you can't do that, excavate good soil and rock from elsewhere and use it to armour and raise the trail surface above the surrounding terrain. This is sometimes referred to as raised trail bed construction, causeways, turnpikes, etc. Google and you will find some good articles about this on the IMBA and other websites.

    What does good soil look like? It should be gritty to the touch and can be squeezed into a nice ball when moist. When dry, it should not form clods that are hard to break and crumble (too much clay). Around here, the good stuff is red-brown and referred to as mineral soil or "gold".

    Cheers.

  10. #10
    OriginalDonk
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    Your natural/undisturbed soil condition is going to vary significantly base on location and your geologic setting. A good place to start would be to see what the National Resource Conservation Service (NRCS) (a branch of USDA) has classified your soils as. Track down your trail area in the Google Maps interface (API) and see what's been identified. There's a lot of information in the soil survey but keep in mind that it was completed at a pretty coarse scale and may not account for site-specific heterogeneity. Here's the link: Soil Web via Gmaps! . Each soil group will have a name that should help (you're looking for loam, sandy loam, or clay loam). If you want to get into it more I can help interpret a few more data fields. You may also want to make a note of the drainage class.

    Your topsoil is called the A-Horizon and, as stated above, will have all of your organic matter. Below your A-Horizon is your B-Horizon or subsoil. The depth of your A-Horizon is going to vary significantly based on geology, vegetation, and your climate regime. In the Northwest your A-Horizon could be 3 feet deep or more so you're going to be building your trail in that zone that may get nasty quickly as the organic material retains water. In the arid Southwest your A-horizon could be an inch or less. It'd be worth seeing what your subsoil looks like. It may be what you're looking for.

    In the end, you've got to work with what parent material you have. Amending (mixing in or altering soil) is going to be costly and really tough. If that's the case and you want sick berms you're going to have to fall back to compaction. When you know it's going to be dry build a berm backbone of 6 inch rocks and place soil in your tentative berm shape and get an endless line of people to come rail the section and pack it down. Hope that your soil has enough cohesiveness that it stays when the weather changes and the rains come.

    Good luck.

  11. #11
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    Quote Originally Posted by ray.vermette View Post
    I've though about it a bit and I suspect what the OP meant by top soil is the top layer of soil with a high percentage of organic material -- dead and decaying plants and such. It's not good as a trail surface as it retains moisture and quickly turns into muddy snot that takes forever to dry up. I don't know how you turn that into something useful.

    You need to dig down past that layer to find good soil for your trail bed. If you are on a flat surface, that's not practical, because you just end up digging a water-collecting trench. This is one of the reasons why IMBA recommends bench cut on sloping terrain. If done correctly, you dig down past the organic layer to find good non-organic soil to build your trail on, broadcast the excavated organic layer downhill, and if everything is done right, rain water will sheet down the hill and across the trail and not collect on the trail.

    Sometimes you don't have much sloping terrain to work with and everywhere you look is flat. If that's the case, you need to work the micro variations in the terrain. Route your trail across every slight bump and high point you can find. When you can't do that, excavate good soil and rock from elsewhere and use it to armour and raise the trail surface above the surrounding terrain..
    "OriginalDonk said Your topsoil is called the A-Horizon and, as stated above, will have all of your organic matter. Below your A-Horizon is your B-Horizon or subsoil. The depth of your A-Horizon is going to vary significantly based on geology, vegetation, and your climate regime. In the Northwest your A-Horizon could be 3 feet deep or more so you're going to be building your trail in that zone that may get nasty quickly as the organic material retains water. In the arid Southwest your A-horizon could be an inch or less. It'd be worth seeing what your subsoil looks like. It may be what you're looking for.

    In the end, you've got to work with what parent material you have. Amending (mixing in or altering soil) is going to be costly and really tough. If that's the case and you want sick berms you're going to have to fall back to compaction. When you know it's going to be dry build a berm backbone of 6 inch rocks and place soil in your tentative berm shape and get an endless line of people to come rail the section and pack it down. Hope that your soil has enough cohesiveness that it stays when the weather changes and the rains come.

    Good luck."

    I like both of these summaries. Thing is if you cannot bring building materials to the trail, you have to think out not just where the trail will go, but how the land wants you to build or modify (in the case of old trail gone bad). Sometimes the materials you need aren't there. Maybe the trail should be built differently then? If rock is needed and not in the available "soil", then is there an alternate trail route. If the soil will turn to slop with every rainfall, then are there enough small stones available locally to push into the soil to solidify it over time? If yes, then why armour with larger rocks you may need further up trail, plus you won't need extra soil to fill in between the large rocks.

    Unless you are building in a very difficult location, or with machines, the soil horizons will have to blend into good trail tread. In the end it won't matter what horizon is where, because good trail will use several horizons or only one depending on local need.

    The fun part is finding the right horizon/s.........

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