Grading Wet Clay 2

[shreve17]

I'm hoping for some advice on the best approach to final grading my lot (just built a new house on it) which is completely covered with at least 12" plastic soil which has been soaked with lots of rain. I have been waiting for a few consecutive days of sun to dry it out so the bobcat could work it but I haven't had any luck. I get one, maybe two days of sun but it's not enough to dry it out and make it workable (with a rubber tire machine, at least, which keeps getting stuck and sinking in areas where water has sat). I'm not looking for any structural solutions, just a way to work it to final grade to get drainage and lay sod on it. Are there any amendments that would help this process? Would a track machine do a better job?

I'm also thinking about mixing topsoil in with it to help the grass grow. Should I do that during final grading to mix it in with the clay or final grade and spread the topsoil on top of the clay?

Thanks

 

[Focht3]

I'd use hydrated lime to modify the wet plastic clay - it will change the soil so that it is less affected by changes in water content. But the presence of the lime will make it hard to grow grass within this mixture for some time. The time frame will depend on the clay and how much lime you use.

Have a contractor do this - be sure he uses an agricultural discing unit to get a good mix. Some of the lime should be applied and mixed in, then left for 12 to 24 hours. The balance can then be applied and mixed in WELL.

How much lime? It depends on the soil. Running a lime series is usually best, but isn't necessary for your situation. You can estimate it using 5% of the soil's Liquid Limit, or 10% of the Plasticity Index, whichever is higher. You don't need to achieve a PI of 20 or less - you only need a "stable" clay.

Put the topsoil on top of the clay. Mixing it into the wet clay will be a real mess, and could end up costing you a lot more in the long run -



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[SirAl]

If you are dealing strictly with landscaping, I would be inclined to have the lot graded using a track mounted loader. Back blading the fill with the bucket and a few passes with the tracks should help to smooth the surface that will improve surface drainage. If it were my lot, I would leave the sod for a season to allow for inevitable settlements of the fill to develop, particularly adjacent to the house. You can then fine tune the grading when sodding your lot. As Focht3 recommends, do not mix the topsoil with the clay.

 

[shreve17]

Thanks to both FOCHT3 and SirAl. I will try a combination of your collective advice. I will use the hydrated lime for the particularly sloshy areas and depend on the track loader for the rest.

To SirAl: To get my Residential Use Permit, I will need to have the soil stabilized. To make sure I understand you, are you suggesting seed and straw until next season and then apply the sod?

 

[SirAl]

shreve17

I don't see any point in applying seed and straw if you intend on placing sod. I now get the picture that your lot will require some form of finished product in order for you to obtain a permit. I guess my advise is of limited value to your situation. Depending upon your location the autumn season may bring deminshing daylight hours, cooler temperatures, and unstable weather - not exactly a recipe for drying. As time may not be on your side, stabilization may be helpful for you to obtain a workable surface upon which to place your sod. In this regard, Focht3's advice appears to be pretty good. I would also talk to a lawn & garden specialist to determine the potential impact of lime on the future vegetation.

Focht3
Good 'Rules of Thumb' for lime application for this situation