Removing Organic materail
Removing Organic materail
(OP)
I am in the process of building a home and have had a soil boring test done which has come back telling us we have orgainic material or "muck" about 7 feet down and about two and a half feet thick. We have companies come in to quote us on removing the material and our bids are over 50,000 dollars. The area to be cleaned out would be about 2500 square feet. We have checked on pilings and they are running around 50K as well. Could we possibly pump concrete or do something else that would be a lot less expensive? Any help would be greatly appreciated.





RE: Removing Organic materail
Realize that you may need to add extra rebar in the foundation walls and may be spread the footings. This is typically 3 grand. So in total around 11 grand. Good luck. By the way, when they backfill the exterior basement walls, have them exclude the muck materials.
RE: Removing Organic materail
A lot depends on these kind of questions. If the fill has been there a long time and is of good quality, you might be able to put your home on a rigid raft-like foundation. You could also dig out and put in a 3 ft crawl space or so - in effect matching the load of your house by the weight of the fill removed. This would be an alternative to the basement which, in a way is a good idea for it will give you a pretty good amount of "room" for later development (shop, in-laws suite, etc.)
It seems that your piles were to be pretty robust. Sadly you aren't in a country with cheap labour - you could do hand dug caissons at 10 or so suitable points, then use grade beams to support your house floor . . . I think that I would have a local geotech review your plans, review the soils data and give you some advice - his cost is much much less than the high figures you have had quoted.
RE: Removing Organic materail
I will try to answer a few of the questions that were posed:
we will not be building a basement, the fill above the muck is standard good fill, the neighborhood was developed in the late 50's so the soil has been undisturbed up to this point in time, the soil beneath the muck is sand and will be fine for building on, muck (in my report from the engineers) is labeled as "organic material", the types of pilings or piers were to be made of some type of less corrosive material than galvanized steel (they wouldn't tell me the exact material). Again, thanks for any suggestions that you may have.
RE: Removing Organic materail
RE: Removing Organic materail
http://www.abchance.com/index.html
or
http://www.atlassys.com/helical.html
RE: Removing Organic materail
RE: Removing Organic materail
I will give you a brief update. I received a quoted for helical piers (I have been waiting a couple of weeks for it) and they want to install 63 piers at a cost of $61,700 dollars. They are basically spreading them about every five feet around the perimeter of my home and under the few weight bearing walls. I had another excavating company suggest that I take my plans (and soil report) back to the engineer who stamped his seal of approval and see if he could modify the foundation to support the home. I have not received my plans back from the engineer but my draftsmen has told me that more than likely he will put in piers around the perimeter and under the weight bearing walls. I am looking at possibly doing this on my own with the help of some friends and someone to auger some holes. My plan is to have a local person come in and auger the holes down to say about twelve feet (based on engineers recomendations). I will then insert probably an eight inch diameter pvc pipe. Rebar will be added and then concrete. I am hoping that this is the route that I am going to go. Does anyone have any suggestions or comments?
RE: Removing Organic materail
I think you will have a problem trying to get concrete to consolidate in an eight inch pipe if there is reinforcing in it. The cage of reinforcing will also get all twisted and/or mis-aligned. Eight inches is kind of small to work with.
RE: Removing Organic materail
RE: Removing Organic materail
RE: Removing Organic materail
Below the muck is the good typical sandy soil you would expect to be there. When they did the soil test they went down to 20' and didn't run into anything unusual. I hope to hear back from the engineer this week and will suggest the steel and concrete piping to him.
RE: Removing Organic materail
Piles - (I will call mech devices "pushed" or "driven" into the ground to develop skin friction and end bearing)
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The piles that you install whether steel, PVC, segmented concrete piles, etc. will require a large external drive weight of at least 2x the final expected load, if to be installed prior to construction to be of any use. Unless you have access to a pile driver or a vibratory driver, you may not be able to get your piles sufficiently set to develop your long term skin and end bearing requirements.
For a typical one-story house with (a) brick masonry veneer and (b) with a heavily reinforced grade beam structure to span the piles could easily be in excess of 1500 plf. you get to play a game with depth of beam to limit you span deflections to L/600 between supports versus the cost of the piles. Most commonly the economic break in the pricing will be between 8 and 14 feet, depending on local labor and material costs. thus if I did the math right, for a final load of around 7.5T you will need an available driving force of at least 15T if not more typically to 20T to provide the crowd on the pile to be driven hydraulically get it to set with a reduced risk of future settlement of the pile.
Spread Footings:
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Depending on depth to strata, you may have the option of excavating only the material required to install the spread footings. However in FL the labor rate may not make this an economically attractive. But by only excavating the footings, you limit the amount of excavations cost required. You will still have a type IV foundation system, except you will use the existing remaining soil as a form and your final loads will be transferred to the sand below.
Piers (mech products installed by means of drilling, auguring, etc)
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These are by far the most common pre-construction support systems. The drilled shaft C.I.P., the helical, ebo-rods, etc are controlled by other factors other than the total "push" load. Depending where in FL, you should have good success with either the Drilled shafts or the helical. The recent price increases in steel have made the use of steel products such as helical piers less desirable economically than at the beginning of the year due to several oversea demands for steel here in the states. The cost for truck mounted installation of these pier systems should be more economical than repair product because of the reduction in labor by using the truck mounted equipment.
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Advice - not asked for but given anyway
A. I specialize in diagnostic and repair. I can tell you from years of repair experience that an improperly designed pile and/or pier under a foundation is no significant improvement over just having a slab-on-ground (SOG)design -- you just paid more for the foundation.
B. This is the one of those times in the construction of a house where having an experienced contractor install the “right” product will be a money saver downstream otherwise you may wish to locate your house (Investment) elsewhere.
C. The most expensive foundation repair costs are derived from fixing foundations which already have had piers/piles installed.
D. If your designing your own layout, try to balance your pier loads bewteen the interior and exterior piers to limit your settlement induced deflections.
E. Find out if your going to be designing that foundation for conventional "stick frame" or "modular"/"Truss" design. Makes a small difference on how you want your interior piles placed/spaced.
Homer Parker PE
RE: Removing Organic materail
I agree that the right contractor for the right system is best but it seems that the price of the right system the right contractor wants to install is going to cost 1/3 of the house! That's expensive. I know that I wouldn't want to pay that much. We drove 100 wood piles in Northern Ontario for only $50k US back a few years ago. But that was a school addition and there is more money in that.
RE: Removing Organic materail
We have a local company called Geopier that installs stone columns that we've used for projects with smaller budgets. The process uses crushed rock instead of concrete, and doesn't involve specialized equipment for installation (a simple track-mounted auger and point compactor), both of which make the cost significantly cheaper. I should mention this is a different process than Hayward Baker uses, as equipment is more sophistocated, and requires more monitoring and inspection.
I don't know that you have the service available in Florida, but it might be worth a look.
http://www.geopiers.com/