At the risk of oversimplifying the solution to your problem, you will need to bring in a volume of clean fill to at least equal what was removed. Use the formula for determining volume of irregular shapes as a method for estimating how many cubic yards are needed to fill the depressions - actually quite simple.

Not knowing the area involved, chances are, it would be more economical to have soil delivered than to use 40 lb bags of top soil. It's also important to compact the soil in layers, or lifts, to match the compaction rate of the surrounding ground. Otherwise, nature will eventually do it for you - as you've just witnessed.

Al with all due respect, how can you state that:

"It's unlikely that it has anything to do with not having enough soil to fill the hole" ?

If the soil was not compacted during filling - they did not use enough soil. The newly filled area has greater aeration, due to the fact that it was not compacted to match the compaction level of the surrounding earth.

My humble apologies. I must have stopped reading before I got to the end of your post and was too hasty in replying. I would have worded my reply differently so that your observation about compaction was properly acknowledged.

I will still say though, that while mechanical compacting would certainly make a difference in how much water retention there would be (or not be) in the disturbed soil, it's doubtful that it would cure the poor drainage issue and the bathtub effect entirely, especially in consideration of the addition of what was probably a sandy topsoil (bags). If the surrounding soil drained freely, he wouldn't be having the issue described to the degree described, so assured drainage via the methods I suggested would still be a more positive solution.

Even though I didn't notice your comment about mechanically compacting the soil, I would still have offered the opinion that it probably wouldn't solve the issue entirely whether the soil level in the hole was concave or convex as compared to surrounding soil levels, but assured drainage (as in a tile, French drain, trench/ditch would.

Al

No apologies required Al - it's the Internet! If we were all talking face-to-face, points would be better clarified instead of being misconstrued. I have been faulted many times in forums by jumping to conclusions, through this faulted communication medium.

Also, and unfortunately with these forums, there's no way to go back and make corrections to our posts . . . at least not to my limited knowledge here. What is written here is eternally cast in cyberspace- or so it seems. :)

What your soil needs is a lot of organic matter, compost, tree leaves, garden waste, something to fill in the pore spaces and aid in stabilizing that soil.

That well-worn mantra is not true in this case, Kimmsr. Additional organic matter will exacerbate the problem unless he's able to amend the surrounding soil too - so it drains at least as well or better than the bowl he's created and the water in the soil has somewhere to drain to.

Al

Hello all, thank you for the replies. You are quite right that we didn't take the time to compact the soil as we replaced it. The additional topsoil was mounded up high and is now, after alot of rain, level with the surrounding soil, so maybe it is compacting itself. The soil that we dug up was very hard(though I don't think we have clay here in New York), full of tree roots and lots of rocks, large and small, so we probably erred in not tamping down the soil we replaced. I may look for some clean fill anyway to add some native soil back to the area. Thanks again for all the input.

There is clay in New York as well as sand and loam and many other soil types. No matter what any soil without organic matter is not real soil, and as the NRCS will tell you the major problem with soils in the USA is the lack of organic matter in the soils. The professors of soil science at both Michigan State University and the University of Michigan will tell you the same thing as will the same people at Cornell.

Again, you are trying to apply your pet answer to everything in sight; and here, again, it is not appropriate. The OPs problem is related to the bathtub effect and occurred because A) He disturbed the soil and replaced it w/o compacting it, and B) He added what is likely a soil comprised of larger particles than the native soil. Perhaps it even had a fair fraction of organic matter in it. You are talking about the soils suitability for growing things and the discussion centers around the physics of water behavior in soils - how he made "quicksand". Adding organic matter to the 'bathtub' created will only make the problem worse. Have you ever seen a compost puddle? It looks remarkably like quicksand.

The soil scientists at any university would recognize immediately what is being discussed and address their comments to the actual topic and not view the discussion as an opportunity to offer darling suggestions like "Add more organic matter" or "Get a soil test". There actually does occur the rare case in gardening where the answer isn't one of your treasured two.

Al

Al, does the bathtub effect happen when one creates a garden by tilling just an area in that kind of soil? Can the problem be mitigated by tilling a 'larger bathtub'? What about soil that is changed from the surrounding soil by the addition of organic matter? Does it also create a bathtub?

I created a "bathtub" when I first dug my beds and it's largely corrected itself just by settling. It took a year or so, though. OP added amendments that, except for drainage issues, are just what a healthy garden soil needs. It might be best to plant moisture-loving perennials on the downhill edge (or in strips if the area is flat) and avoid walking in the beds, especially after a rain.

The bathtub effect occurs when water accumulates in one fairly small place because it cannot flow through the compacted soil that surrounds that heavily amended place. Most often this will be in clay soils where someone will add lots of organic matter to a 4 x 4 planting hole and not the rest of the area, although it may happen in sandy soils where there is some hardpan. Adding organic matter to any soils helps the Soil Food web, the wee critters that live in and work in your soil, by providing them a food source so they can do what they do open that soil up so moisture can flow better, plant roots can move about more freely, and those plant roots can have access to the nutrients the soil holds.

CC - Kimmsrs is on track now and his answer is fairly accurate, but in this case adding organic matter to the disturbed soil will compound the drainage problem - sort of like enriching the soil but killing the plants in the process. It makes no sense.

When you till a plot, drainage can be affected by the fact the soil is comprised of fine particulates, or it can be affected because there is an impermeable substrata below your soil that impedes percolation. The latter is usually only a problem where your soil also has poor percolation AND you are on flat ground. If you were on a hill, the water would move laterally in the soil until it actually exits the soil and flows downhill - similar to a river rapids or waterfall, only not as dramatic.

Neither will amending the surrounding soil with organic matter improve drainage of your plot, unless the water can flow THROUGH the amended soil and be channeled away by gravitational movement (downhill - tile/drain/ditch) or be removed mechanically (pump).

When you dig a hole & disturb/amend the soil in it, the hole will be a water trap unless the surrounding soil allows movement of water through it. How seriously the trap plays into plant vitality/viability depends wholly on the speed of percolation or the provisions you've made for drainage.

BTW - it would be difficult to support the idea that "No matter what any soil [sic] without organic matter is not real soil ....", even within the context of this forum/thread. How does that work? It is dirt (or something else) until someone in charge passes judgment that it now has enough organic matter - then it's soil? C'mon.

Al

Bagged topsoil (around here, and when I lived in NY) is sandy and silty and turns to sticky muck when it gets wet. Bagged topsoil often starts out as river bottom sediment. Tilling it into native clay rich soil may be a good way to help solve the problem. I have a couple of small raised beds filled with bagged topsoil and they get mucky when watered (even when the soil below them is still dry). I can just imagine what it would be like if I tried to fill in a hole in the yard with the stuff.

When filling in a hole in the middle of an area of not particularly well percolating soil, I wonder if before adding any dirt that using a potato or broadbeam fork to break up the subsoil [subsoiling]would help downward percolation in said hole.

Wayne - that would assume that you were somehow "poking a hole in a liner" and that the soil below would somehow drain better. The odds of that happening would be so remote as to be considered nonexistant. Once again, the water in the depression has to have somewhere to go - downward or laterally by percolation, or into a ditch/tile/drain where it can be removed by gravity flow or mechanically. If the surrounding soil drains well, the degree to which the scenario might be a problem varies inversely with with improved drainage.

Al

I would let it go over winter I bet its a lot better in the spring after it has settled in
It really has nothing to do with bathtub drains or organic matter

Then the question arises: Tiling of wet areas in fields may go 2,3,4, or so feet deep. To drain with tile water must be able to percolate below some amount of subsoil or it would not be helpful.

Also, how do wells get recharged and the water table replenished? It would seem to me that large areas of soil must be percolating to some defree. I don't think that the ground water all gets there through a few "cracks."

When you're talking about plants, you need to speak about percolation rates in terms of hours, not days or weeks. Of course water percolates through clay under specific circumstances, so the groundwater would eventually be fed.

In the case of a tile, the tile would run through the tilled area, making percolation through surrounding soil a nonissue.

Jonas - the issue of waiting was addressed way up thread, but the problem is immediate. We KNOW that waiting is an option that will resolve the issue eventually. The 'bathtub effect' is inextricably attached to the conversation because it's a well-known description what the problem actually is. To say that the issue has nothing to do with the 'bathtub effect' is to say there is no problem to begin with, which we know is not the case.

Organic matter is secondary to the degree that it only exacerbates the problem.

Al

"Topsoil" is the top 4 to 6 inches of soil. What is sold in bags labeled "Topsoil" can be anything and most of it is not worth the price charged. What I have found over a long period of time is that most people expect "topsoil" to be that type of soil known as loam. What distinguishes good topsoil from not very good topsoil is the amount of organic matter in that soil.
Whether you will see that "bathtub" affect or not will depend on how water moves through your soil, because if it does not move easily you could have a bathtub, some place where water accumulates. One very expensive method of alleviating that problem is to install drain tiles, but the best method is to get sufficient levels of organic matter into that soil which will then open the soil up so water will flow more freely.

"Whether you will see that "bathtub" affect or not will depend on how water moves through your soil, because if it does not move easily you could have a bathtub, some place where water accumulates."

Well, yeah! This is what we've been talking about from the very beginning, so it's hardly enlightening .... and I'm not sure why we need to go on a tangent and take in the elementary lesson about topsoil, but ....

".... but the best method is to get sufficient levels of organic matter into that soil which will then open the soil up so water will flow more freely."

Sorry, but that is wishful thinking. For at least this singular thread, you need to let go of the idea that adding organic matter is the cure for all ills. If you are dealing with the problem of a bathtub effect in the middle of thousands and thousands of acres of a soil type that drains poorly, do you really expect the gardener to amend the entire surrounding acreage? Even if he is dealing with a relatively SMALL plot of ground, like a lot that has been stripped of topsoil so that he is growing in clay, it's STILL not reasonable to think that someone will haul in compost by the double-bottom load and incorporate it in the entire volume of surrounding soil so his garden can drain.

BTW - if the water has someplace to flow TO, installing $50 worth of drain tile will be a heckofalot less expensive than buying, trucking, and incorporating hundreds, if not thousands of yards of compost into the surrounding soil - which in many cases would only be building a bigger bathtub.

No one argues that having a plentiful presence of organic matter in the soil is a good thing, but to habitually ignore other primary factors in favor of promoting a rigid ideology as the answer to everything is, at a minimum, imprudent.

Al