My native soil in the yard is silty/clay loam. I am not sure if this is truly native or fill dirt by the builder decades ago. We had issues with soggy lawn and removed 4-5 inches of soil + sod and put French drain grid.
Now, I want to backfill the area which was dug up and hauled away, I was thinking about getting topsoil which the soil place says is sandy loam. They also have 50-50 mix of sandy loam soil and compost. Which one is the best option for something like 10" of back fill. If I go with 50-50 blend the compost will eventually decompose, does it means I should add 2-3 inch more soil now to factor for setting.
Contractor said roto-tilling, but I am worried that would do more harm than good because the area is wet and has some compaction due to running bobcat/excavator and we are not looking at it drying out until may or June.
Is the black filter cloth covering your French drains? Are they pervious pipe or just granular trenches? Did the French drain solve drainage or is there ponding during rains? Chances are you have a hardpan under the material the builder brought in, but if it’s deep enough and you don’t get ponding, then you can always add more topsoil or compost. Is your intent to have only lawn here?
Dennis
Kent, wa
Filter fabric lining the trench > River rock > 4" PVC pipe with holes > River rock wrapped back in filter fabric.
We don’t know whether is fully working but I know water is flowing through the drain and due to removing the soil the area is a bowl and need to be bought back to grade surrounding it and seed grass or lay sod.
The only reservation I would have if it were my decision, is whether you have actually and to you satisfaction solved drainage? If you are certain that’s solved, then I can think of no other reason you should not add more.
Dennis
we still have 2 months of rain, and I don’t plant to seed grass or lay sod close to summer. If drainage is not solved then the contractor should fix it. reason I want to add few inches more is to avoid having to repot grass in 2-3 years to add few more inch dirt due to settling/decomposition of compost. The sandy loam is from a pit in WA, Its Dallesport series rated as excessively drained and low runoff.
Do you have any idea how to make a well around existing tree trunks when adding the soil to elevate the grade. I have seen people building huge wells 2 or 3 ft in diameter, but my area is pretty small wondering if there is some form of readily available product.
I am a kind of professional landscaper being that I install and tend orchards for a living, along with maintaining a small bearing age fruit tree nursery. I know enough to realize the importance of adequate drainage and also that most landscape professionals, at least around here, tend to do a poor job of solving drainage problems and that French drains are not always very effective- even when there is sufficient slope to use gravity for drainage.
You have already invested a great deal in this project, but have you consulted with a soil drainage expert? There is a field of business whose entire focus is solving residential drainage issues- if you can find one with a good reputation I suggest you at least pay for a consultation, because that is what I’d do.
Lucky for me, my customers with poor drainage have almost always been willing to plant their orchards on mounds for each individual tree, which is generally effective. I agree with your landscaper that mixing in your original soil with your amending soil, especially if it is half compost, would be the best, but it requires a very powerful tiller to affectively mix a heavy soil with a much lighter, coarser one and is almost impossible with a wet clay with any equipment I’ve ever used besides a heavy cultivating fork and agonizing labor. However, a topsoil that gradually moves from coarse to fine as you go deeper does a better job of holding available water and anchoring trees.
If you are able to add a full 10 inches it might alleviate your problem whether the French drains work or not- I believe they eventually get clogged in any case as fine silt gradually penetrates the fabric (but ask an expert). I doubt a nice lawn would require that much, even if the compost in a 50-50 mix shrinks over time.
In respect to your landscaper, I should add, that he may well know exactly what he’s doing- I’ve never seen a French drain in a grid before, so I haven’t a clue, but it looks like it might work- as long as gravity is sufficient to pull the water out of the soil and water isn’t being trapped on your property in a way it can’t escape without a special system… .
