I would not mix anything into it until a soil analysis is done. They are not that expensive, and are indispensible for a situation like yours. No one can really know what your soil needs if it has already been amended, possibly incorrectly.

Cheers,
Michelle

For poorly draining or heavy/compacted soil, a soil test is unnecessary and really won't tell you what you need to know. Soil tests generally assess the nutrient content of soils, pH and sometimes the percentage of organic matter. But none of that will explain why a soil doesn't drain well. That has to do with soil texture and structure and is most often improved or alleviated by adding materials that have a larger, coarser texture and offer greater porosity. In a word (or two) - organic matter. Incorporating quantities of organic matter - often compost, sometimes special, bark-based clay-busting mixes - is the tried and true method of improving soil drainage.

In the PNW, planting mixes (typically some combination of topsoil/loam, screened compost, sand, sawdust and/or peat) are often brought in to create planting beds or in prep for lawns. Although they are pretty decent soils with the ability for healthy plant growth, the particle size tends to be too uniform and if it is just being applied to the top of already heavy or clay soils, it does nothing to encourage better drainage unless the thickness of the added soil is significant.

Why is this soil draining poorly? What is the cause of that poor drainage? Are there soil nutrients that are in extreme excess that have bound together to prevent easy movement of water? Has there been some chemical reaction that produced hardpan? Is this soil thick clay with no organic matter that is simply impervious to water flow?
Adding organic matter is a start toward improving that soil, and the drainage, provided enough organic matter is added. A soil test can be helpful, too.

Oh gardengal48 I do disagree. Often times (but not always) a soil test can tell you why your soil is not drainaing properly. If you have and elevated sodium adsorption ratio (SAR), particularly in a heavy soil with high clay content, the balance of soluble sodium to calcium and magnesium can be so far off that proper soil structure doesn't form and drainage can be severely impeded. Also consider the fact that many soil tests also include particle size distribution. If the particle sizes are widely distributed, (particularly when evaluating ratios of very fine sand to fine sand, to medium sand, to....) the soil is more prone to compact, and that can provide another clue.
Back to the original point of the thread. I'm a little concerned about the heavy import soil. I am wondering what the texture of the native soil underneath is. If a heavy soil is placed on top of a significantly coarser material, there can be drainage problems at the interface that results in a situation where water will "perch". That can create a zone of saturation that remains wet for an extended period of time which can lead to anaerobic soil conditions. With that in mind, I have to wonder if the "manure" you smell is healthy or not. Usually an "earthy" smell is good. "manure", "sewage" or "rotten egg" smells might mean anaerobic activity. If that is the case in your situation, well, it's tough to say what will happen. I would try to dig down to see how different the textures of the native and import topsoil are so that you know what you're dealing with. Then I'd have that soil test done to check the SAR to see if gypsum will help. (if sodium is already properly balanced by calcium and magnesium, gypsum will do nothing but raise your salinity). Then I would physically break up the soil. I would not try adding sand because you can introduce that wide particle size distribution I was talking about earlier and/or create a situation where clay balls up within the sand so that you have little pockets of anaerobic activity. Those balls of clay that stay wet can also act as little micro environments that remain wet and harbor the pathogens responsible for root diseases. As far as adding organic, that might help if it's low but if it's already high, you might make the situation worse. A soil test can tell you this as well. Again, it just depends on which test you get.
In the mean time, whatever the situation, be sure to monitor all irrigations carefully by digging down and checking the moisture of the entire root zone to avoid over and under watering.

Gypsum is only valuable for sodic soils, which are NOT present in the PNW. Poor drainage here is nearly always attributed to a) high water tables, or b) clay-based soils. Layering but not incorporating a uniform particle sized imported soil over a clay base does set up significant interface issues and will not improve or correct drainage. Just a careful look at one's soil profile will provide ample evidence without the need for a soil test. In my professional career, I've yet to encounter a poorly draining NW soil that was not improved by amending with organic matter or altering the water table through drainage systems or raising the soil level.

I've seen sodic soils from Oregon to Mexico and everywhere in between. Even in areas where high precipitation provides ample leaching to flush sodium out of the root zone under normal conditions, it can happen when soils are over amended with too much manure, biosolid product, or horse bedding, all of which typically have a whole lot of sodium if not leached properly on the production end. I've even seen the situation come about in one very special case, with a gross over-application of sodium nitrate. Also, if sodium is comparatively low but the parent material of the mineral fraction results in a low calcium/magnesium soil, an imbalance can occur. But sodicity shows up in any soil test that includes extractable cations. All you need is soluble calcium, magnesium and sodium in meq/l (aka. millimohs per cm) to calculate the ratio. Sodicity can lock up a soil like nobody's business and I've seen it happen time and again. That's exactly the sort of thing that can get picked up in a soil test, particularly in a heavy soil with high clay percentage that provides plenty of cation exchange sites. (if you don't test for it, that may explain why you've never seen it)
Also, if you have a soil with 20% organic content by total sample dry weight (not by volume) down to 15 inches in the profile, are you seriously trying to tell me that adding more will improve drainage? No, seriously?
I'm not saying that texture and subsoil drainage have nothing to do with it. In fact, they played a starring role in my first post. My point is that none of us here knows what the previous owner put in the soil and to ignore soil chemistry when considering the possible factors would be a mistake. (one commonly referred to as "tunnel vision")

You said that the topsoil was brought in and usually they overkill to compensate for whats already there. In this case possibly sand is underneath and just tilling will mix it up and connect you with drainage. OM is fine but will not last forever. Sod mineralizes over time.
I know there may be some who go bonkers over the idea of adding sand , but that is how your natural soils were blended for thousands of years and they are still the best today. good luck:)

I wonder if the fact that 'Bonkers' was my favorite board game as a kid means anything.
Anyway, I am a big opponent of adding sand for a couple of reasons. Mother nature did not add sand to clay (or vice versa) and mix it in with a rototiller. The blend is not homogenous enough. Also, moisture is your enemy when mixing sand, silt and clay. Uneven mixing and moisture cause clay to stick together in those little balls that cause problems. You can do it correctly, but most people aren't willing to excavate their soil and spread it out to dry, then do the same with their import, then put them into a commercial mixer (or a cement mixer) and blend them until the mix is uniform. I've seen some homeowners do it and if done right it can work. In fact, I work with commercial providers who do it successfully as a matter of course. But that's a big chunk of their business and they have it down pat. And, even if you do it right, you can still have a problem if you don't know the particle sizes of both your native and import. Just throwing sand in without knowing the particle size distribution of both materials is, quite literally, a gamble. I've also seen a number of situations where people only thought they were successful. For example, they amend their soil with sand, plant vegetables, and have great luck. Of course, those little clay balls are in the ground going anaerobic and harboring diseases, but by the time the plants are really sick, they've produced and they get yanked. The homeowner is happy. Little does the person know that the plants would have produced for another month if they hadn't become diseased. They also find it quite shocking when the roots of a nearby tree susceptible to Phytophthora and/or Armillaria grows into their vegetable garden 20 feet away, hits those little festering pockets and picks up a nasty root rot. Shocking, that is, if they even believe it. Try telling someone that their coast live oak is dying because their vegetable garden has a problem when their tomatoes look healthy. It's true, but man is it tough to get some folks to understand what's actually happening.

You need advice from people who know Washington soils.

If you're in Western Washington, you do not have an excess of minerals, particularly not of sodium, causing your drainage problems. Eastern Washington, maybe.

If you're in the Puget Sound area (why oh why do you not specify where you are on your member page????) you probably have native soil that is mostly gravel and sand. When you squeeze a handful, does it squish into a sticky ball that does not crumble? if not it's not a 'heavy' or clayey soil.

Here's what I think may be going on (IF you're in the Puget Sound area! the rest of Western WA has unglaciated soils that are not nearly as gravelly and sandy as ours). You have 'topsoil' that may be of decent texture, but a relatively thin layer plunked down on top of gravelly sandy glacial till. Any time you have a drastic change of soil texture you block water drainage. Does not matter if the lower soil is better or worse draining. The change is what blocks the water movement.

Clay soils are rare around here. I've seen pockets of clay, and outwash soils that have some clay in them and seem clayey in comparison with the sandy soils that are more typical, but I would not expect you have an actual clay soil in your topsoil. So I think your topsoil is probably decent soil but needs that boundary layer underneath it broken up.

We do get hardpans here, usually glacial in origin, not chemical as in other areas. You won't be able to break up the glacial hardpan - how could you undo what the weight of a glacier has done??? forget it! Shallow soils on bedrock too.

What I would do is lay on some compost, get the biggest tiller you can handle, and till down until you get past the topsoil and into the native soil to break up that boundary. Do not add any chemicals or fertilizer or sand or manure. Just compost. Unless of course it's on a hardpan or bedrock, then you'll need to raise it up more.

Re: Squonnk... "Also, moisture is your enemy when mixing sand, silt and clay. Uneven mixing and moisture cause clay to stick together in those little balls that cause problems".

I never got to play Bonkers when I was a kid. I played with sticks and on a good day I would find various plastics along the road :)
I have been sittin on clay on this part of the farm for 11 years now. When I planted the apple trees I had to go 3-4 feet deep to get to the sand and gravel below. Where the Blueberries are - only 1' or so. I put the OM right at the bottom of the hole and alternately refill with sand and the clay. Add the compost as I stir it up for final texturizing, plant, and cover with wood chips. Had great success and I am even able to do flood irrigation in all areas.
My belief is those clay balls will always be clay balls if never exposed to another material to mix with. In many of my tilled gardens the mix is now homogenous. I create the soil environment for lots of worms and I attribute the success more to them, frost, and roots than to my tiller.
I am better with mechanical drainage than the chemistry of it. I do like to increase knowledge in that area.

Most usually when people add sand to clay, or vice versa, to "improve" their soil they simply do not add enough to do any good. Every Ag School that has written anything about adding sand to clay recommends at a minimum 45 percent sand by volume, except Cornell (and one other that I do not recall off hand) which recommends 75 percent. A little bit of sand will creat more problems then it will solve, but adding a little sand may not necessarily create concrete because that depends on which clay you have.
So if you are planing to add sand to your clay to improve drainage plan of getting many truckloads, and tilling really deep.
Organic matter, which does not "disappear", is digested by soil bacteria and that means you do need to keep adding more, but that is why Ma Nature provides so many sources of organic matter, every plant that grows is a potential source of OM. That we do not utilize that material is our fault, our ignorance.

Wow - impressive input by all. As a new member to this site, I was under the impression that I would receive an email when someone posted a response. Since that did not happen, it took me a little bit to check back. Now that I'm here, I have WAY more information than I had even hoped for (thanks to all). REG_PNW7...thanks for the tip of adding my location - that's done now. For the benefit of this thread, we live on Finn Hill where Bothell, Kenmore, and Kirkland all meet. To address your other question, the soil in question does stay in a sticky ball when squeezed together and doesn't crumble.

So to summarize the input, I should consider either amending the soil with compost or lots of sand, and it wouldn't necessarily be a bad idea to have the soil tested. If I've missed anything fundamental, don't hesitate to help course correct. Again - thanks for taking the time to share you knowledge.

Cheers,
Scott

For future reference, if you want to get an email when somebody responds, you need to check the box when you create the original message. Once you click send, you can't go back and check it (or if you checked it and are getting tired of the emails, you can't uncheck it).

RE: kimmsr... Organic matter, which does not "disappear", is digested by soil bacteria and that means you do need to keep adding more, but that is why Ma Nature provides so many sources of organic matter, every plant that grows is a potential source of OM.

If there are plenty of worms to pull it in just the grass clippings can resupply the OM. My only point was that once the stuff is digested under the sod its ability to help drainage is reduced.
If he is lucky there is sand under the topsoil and won't need truck loads brought in.
You are the second person that mentioned that adding sand to clay makes bricks or concrete. Could you elaborate? :)
thanks.

Virtually every reputable soil resource will caution against using sand to improve drainage as it is simply a very inefficient method compared to others. As kimmsr has noted, you have to bring in far too much sand to affect a significant difference - too little will result in more of a brick-like consistancy. And it has to be just the right size of sand particle - too fine a size will not significantly increase pore space and you have defeated your intent.

Adding organic matter can effect long term improvement of soil structure providing one does not undertake excessive tilling or otherwise compact the soil (like working it when it is too wet or the action of repeated mowing and walking, like most lawns receive). There is a point beyond which OM does not decompose further or disappear. In fact, what we most often refer to as OM is in truth organic material rather than organic matter - organic matter is what remains after the decomposition process is complete, essentially a humusy loam. Organic material is that once living product that is in some stage of the decomposition process, ie., less than fully "finished" compost.

What no one has pointed out is that the soil underlying sod or turfgrass generally becomes compacted fairly rapidly, despite its quality to begin with. The constant repetitive actions of mowing (and edging, fertilizing, etc.) as well as the foot traffic lawns get compared to planting beds just encourage this trait. And compaction interfers with drainage. Core aeration on a routine basis, followed by a light topdressing of the OM of your choice will help significantly, both in reducing compaction, introducing additional OM to the soil and allowing oxygen penetration.

I totally agree on the value of OM and how it turns to humus. I have been using it in lawns and gardens for 35 yrs. now.
I guess the idea of too little sand creating a brick like consistancy still confuses me. When I added sand and gravel to the clay driveway it is packed hard but I can still break through in the spring.
On the other hand I have just topdressed a little section of clay lawn with sand and did some overseeding. It looks great and most of the sand has already been assimilated into the ground. Mostly by worms I assume.
Is it possible that there is a difference in a static application (driveway) and a dynamic one such as lawn or garden?
I really am not trying to be difficult it is just that all my experiences with mixing sand clay and OM have been super positive :)
I appreciate your time on this. thank-you

Anytime you add organic matter to soil there is some that does not get digested completely by the soil bacteria and that is humus and when the soil bacteria, and earthworms, pull that into the soil it becomes part of the soils structure as gardengal pointed out. If insufficent organic matter is added to a soil, or if none is added for some time the bacteria will then digest that residual OM, the humus, and then they will go dormant until such time as enough OM is put back into that soil so they have a food source.

Here is a link that might be useful: The Soil Food Web Primer

The article had some new info in it, but I was hoping for one that describes the problems of artificially mixing sand, OM, and clay.
For me it has always been as simple as mixing the rooster and the hen house. Nature takes it course whether I understand every detail or not.
We do enjoy understanding every detail though:)
I remember when questions were not important, survival was.
Research in my open air labratories is actually a luxury.
thanks again.