Thank you so much for posting this question. We have the same problem here. A couple of years ago we had a company bring a truck load of fill dirt and then we shoveled/raked and tried to compensate for the gradual indentation of our yard. Neighbors told us that they too dealt with the same issue and that's how they corrected it. Our neighbors believe that during the construction of the houses in this neighborhood (back in the 50's) builders simply buried construction materials, trash, etc., rather than dispose of it the way they should have.
My husband wants to bring in additional dirt and plant some palms. I'm afraid that this will just "add salt to the wound". I'm thinking that the additional weight will only add to the problem.
This is such a wonderful and helpful forum-I'm sure someone will write back soon and help us both with our dilemma.
Sue.

Hi guys: My name is Karen, and I work for Bechtol Engineering in Deland (between Daytona and Orlando). Among other things, we test soils before and during phases of construction; and one of the biggies is buried organic debris underlying new houses: As the organics decompose, a "void" space the size and shape of the original organic mass is created, the subsoils sink to fill it, and all hell breaks loose in the overlying structure - cracked and flooded foundations, cracked exterior walls, etc...
It's especially common in relatively newly created subdivisions with man-made canals and ponds - the trees and scrub that used to stand in place of all those building pads and water features have to go somewhere, and greedy contractors may look for ways to avoid the high cost of trucking that stuff out and paying landfill fees.
If it's under your house, you can do things (very, very expensive things!) to shore up the foundation; but I know you guys were talking more about your yards. Your best bet would be to call a geotechnical engineering firm near you and have someone come out to do borings. If you need deep borings requiring a truck-mounted drill rig it's very expensive, but if all you need is a guy with a hand auger (typically good enough to get down about 7 feet) it's not. The borings will probably be able to show you where the buried debris is located, and roughly map its vertical and horizontal boundaries for you. If there's no structure overlying the organic deposits, you can just supplement the lowest area inside the boundaries with any cheap fill dirt - make sure you specify that this dirt is just for growing grass & trees, and not to be used for structural subgrade: it'll be half the price, because it won't need to be particularly clean or well-graded.

Talk to a real estate attorney (not one that specializes in only real estate closings). You (and all your neighbors) may have to file an action against the original developer. The attorney will advise you on what you need to obtain as evidence for your case. I would go this route to find out exactly which tests needed to be done in order to prepare for the battle.

Thanks Karen and nativemel for the helpful feedback. Unfortunately for me, I'm not in a position to hire an attorney and as far as trying to locate the original developer, I'm not interested in taking that route.(Besides, they're either dead or bankrupt by now)I'm curious though if it's a good idea to simply add fill dirt, which we've done before and simply plant a garden. Will this extra weight in the discussed area be detrimental to the underlying problem? Should I take into consideration the weight of any trees we choose to plant there? The area in question is far from the house and receives direct southern and full sun exposure.
Thanks again,
Sue.
PS. Should we worry about possible sink holes in the future? There is no runoff from rainfall in the discussed area.

No, the weight of trees and shrubs will have no effect. The weight of a house is so much greater; that's far more of a problem. If a little soil subsidence happens under a tree, the tree and it's rootball will simply subside a little right along with it, and probably show no ill effects.

As for sinkholes - yes, absolutely. There's nowhere you can go in Florida to get away from potential sinkholes, and they're nearly impossible to predict because the problem often starts so far underground. There's really nothing to do about them but wait until they've done all the sinking they care to do, and try to rebuild.

If you go for the fill dirt option, again; just ask for the cheapest, lowest grade of fill material - you don't need anything fancy to beef up a yard area; and you can often buy the very dirt the contractors and developers are paying to have hauled off their project sites. For roadways and large buildings, you often have to import soils and soil-rock-clay mixtures that are cleaner, or have a greater load-bearing capacity, than the "native" materials on site - when they swap out the native sand for fancier stuff, you can take the native sand off their hands pretty cheap. Another potential source of fill materials is paving companies and concrete plants. You're probably not familiar with them, but I'll bet you're within 10 miles of one or both right now - just try the yellow pages. Both of those kinds of facilities keep stockpiles of all sorts of aggregates and soils; they may have some that aren't working out for them.

Wow! Thanks again Karen. You are a gold mine of knowledge and I really appreciate the note back. I'm sure I'm not the only person you've helped out today.
Just goes to show how many knowledgeable and helpful people are members of this site and of this particuliar forum.
Enjoy your day,
Sue.

Very interesting post! Fortunately when we build our home 5 years ago, the developer and builder was brought in for employees and first time home owners. Not only the company we worked for (Bonita Bay Group) but we, also were watchdogs as to the progress and construction of our home. The builder knew of my hubby's construction experience and knew also we would be out every other day. We saw some nightmares in our development. We were very very fortunate.

karen_florida - WELCOME! You are a new face here and you have some incredible knowledge to share!! I hope you will join us more often. We like to enable others in the gardening world...want it?...gotta have it?....BUY IT! lol

Hope you enjoy the forum as much as I do!

Hi,
About 15 years ago someone bought a 2 acre lot that is down the street. They proceeded to "fill " and build a house on one acre ,and the other was filled with more the 10 foot of landscaping debris, Mostly palmetto fronds. When we drove by, it was literality higher than the roof of our truck.

It took about 5-7 years to decompose..... and it looks like a normal lot now. I would look very carefully, and take many core samples on any lot I would buy theses days.

D`Ann

We had the exact same thing happen in our own yard. Developer or builder buried trees. Not knowing what was happening we called our insurance company for fear of sinkholes (Hernando County) and they had an engineering co come out and investigate.

They confirmed that the sinking areas are decomposing trees, but it turns out our soil was very loose under the home, and our insurance co. paid to have our house stabilized by a remediation company. For us it turned out to be a good thing. In a sinkhole prone area, we have the benefit of having been stabilized without having suffered any of the foundation cracks/damage caused by a sinkhole first. Additionally they took all the sand they removed from under the house to make room for the cement and filled up the two depressions for me. I have a garden over one spot, and compost area over the other.

The worst thing that happened for us during the whole process is they killed our gardenia.

On a good note, this county no longer allows debris to be buried...but the county next door still does...scary.

Great information Karen_Florida.

Nat

I'm so glad I was able to help you! Good luck with getting your yard to the elevation you wanted, I hope it all turns out to be not too expensive or too much trouble. By the way, if you wind up having someone excavate more buried organic debris materials from the pond area you mentioned, make sure to tell them to LEAVE THEM, stockpiled somewhere out of the way on your property, if you can. It'll save you the extra man-hours and truck fuel costs they might charge to haul it away, and you'd have the already jump-started beginnings of a really nice composting pile.

I have dealt with many places that had builders dump their extra concrete blocks and stuff in a hole and bury it. If you have organic material breaking down, all you need to do is add some fill. For smaller areas that may have concrete block and materials like that, that are creating small voids, we went in their with a garden hose and a shovel and dug down a little and used the water to flush the voids and to get more of the surrounding sand to fill in the voids. In the same way, you could add some dirt and squirt mud in the voids if the soil is harder. Then once you think you have done all you can, then you add more fill. Not the best way to take care of it, but a cheap way most of us can try to fix things.