Adding 15ft of soil above swamp?

[StructureMan44]

A 10 acre project needs the ground lifted 15ft. The existing site is swampy and directly adjacent to a lagoon. How do I know if (and how deep) the existing swampy soil needs to be cut and filled in order to have a stable surface to add the 15ft? The 10 acre site will hold a small power plant. This is for a very preliminary estimate. From my name you can tell I'm structural and this is way outside my wheelhouse.

 

[greenone]

Wow! Has anyone investigated what permits you need to fill a swamp? That would be my first concern, before the technicalities of how to do it.

 

[rconner]

[enough "soil borings" to be representative would probably be a good start]

 

[Twinkie]

I mean a swamp is a swamp for a reason. If its 10 acres in size, that drainage area to that must be huge, where is all that water going after you fill this thing?

That is a lot of dirt.

 

[bimr]

You have to have a geotechnical investigation or knowledge of the area where the project is located.

If you have information from another project that is located in the same area, that information would be very helpful.

For a power plant, you may be looking at a pile foundation.

 

[nackra]

geotechnical reports should also address "consolidation" of substrata.

We recently constructed an interchange on "soft" soils. The geotechnical report estimated consolidation of 12-inches (90-days) which did occur.

 

[oldestguy]

If the 15 feet of fill is for a "stable surface", it would appear that you really need help of that geotech. Are you expecting a flood and that is to stay above it? If not, reconsider that dimension. Putting all that expense where you won't see it later may not add to the value of the property by much.

 

[JedClampett]

It reminds me of this:

https://www.youtube.com/watch?v=aNaXdLWt17A

 

[msquared48]

What are you going to have to mitigate to fill the swamp? Usually here, for every square foot you fill in, you have to create 2 square feet of wetland (swamp here) in some other location. Sometimes the ratio is worse, depending on the jurisdiction. Sometimes you just can't do it at all.

Mike McCann, PE, SE (WA)

 

[dicksewerrat]

You need a permit from Army Corps of Engineers, State and at least the county to touch the soil. But you probably need an Environmental study to make sure the slimy 8 toed toad doesn't live there. Not to mention those that don't want a power plant near them.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com

 

[Ron]

Two issues...environmental and geotechnical....get both resolved before proceeding or you'll regret it!

 

[beej67]

Three issues, Ron. There's that pesky floodplain as well.

The geotechnical, environmental, permitting, and flooding issues from this project description are so tremendous it makes me think the OP isn't in the United States. But then he goes and measures his area in acres.

I will be interested to see how this thread develops.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[oldestguy]

Looks more like a prank on us.

 

[LittleInch]

Q "How do I know if (and how deep) the existing swampy soil needs to be cut and filled..."

If - It's in the description - "swampy soil" is by definition swampy and therefore not able to support even your foot pressure without sinking so it will need something doing to it

How deep - ~Get a survey. Could be anything from 3 ft to 15 ft. Anything more and you would probably pile it or raft it as the cost is too high. The Victorians knew how to do it -

http://www.engineering-timelines.com/scripts/engineeringItem.asp?id=1150

As said the real issue is not the technical one - its environmental and planning (it was a bit easier in 1820's...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[cvg]

4 issues Ron - #4 structural engineer in charge of the site grading plan...

why isn't there a qualified civil or geotechnical engineer in charge of the site grading and foundation design?

 

[msquared48]

Five issues: Is the proposed structure within the wetland buffer?

Mike McCann, PE, SE (WA)

 

[Ron]

Agree guys....the plot sickens!

That's almost 250,000 cubic yards of fill material, placed as engineered fill...that will take months. Assuming you can compact 1000 sf of soil per hour per lift, you have about 7,000 hours of compaction. That would be almost 4 compactors working full time for a year. Must be a government project.

 

[darthsoilsguy2]

too bad your handle isn't (Nuclear) that would get people up

wetlands i've mucked out have all been the 3 to 4 feet variety. if i had to pick something on a very prelim level, i would go with 4'. for that size an area, you should discuss with the future Geotech about surcharging and settlement monitoring because there will likely be time and materials to do it.

 

[msquared48]

Just build the thing and turn it onto a brothel. The compaction should be achieved rather quickly and at less cost.

Mike McCann, PE, SE (WA)

 

[oldestguy]

Hey Darth Soils: How about 40 to 80 feet of peat?? Yup, we build structures on it. No piles.