levee construction
levee construction
(OP)
I have a levee/river bank protection project in the southwestern United States where a gabion bank lining will be constructed on a normally dry river. This will protect against erosion during periodic flows.
There is some base flow and ground water is maybe a few feet below the surface. The bank lining requires a "toe-down" below the surface to protect against scour. Construction will require excavation, compaction and placement of fabric and gabions or some other type of lining material below the water table. We are trying to determine methods of carrying out this construction, possible costs and other implications.
Existing ground is a mixture of sand, gravel and silt with very little cohesion. Very few boulders exist. All is deposited in layers by periodic flows in the river. Bank slope will probably be 2H:1V or flatter. I prefer not to cutoff or prevent subsurface flow from entering the river, as this is considered "Waters of the US", and doing so would have an adverse effect on the environment.
Ideas we have considered:
1. Dig trench and install sump pumps - cheap but how effective?
2. Install sheet piling, dig trench and install sump pumps - expensive
3. Install wells - expensive, but how effective?
4. Launch the gabions into a wet trench with crane - expensive, difficult?
5. Install sheet pile cutoff at the toe and no excavation - not environmentally friendly
This is a planning study at this point, and I would appreciate any input on cost, feasibility, etc.
There is some base flow and ground water is maybe a few feet below the surface. The bank lining requires a "toe-down" below the surface to protect against scour. Construction will require excavation, compaction and placement of fabric and gabions or some other type of lining material below the water table. We are trying to determine methods of carrying out this construction, possible costs and other implications.
Existing ground is a mixture of sand, gravel and silt with very little cohesion. Very few boulders exist. All is deposited in layers by periodic flows in the river. Bank slope will probably be 2H:1V or flatter. I prefer not to cutoff or prevent subsurface flow from entering the river, as this is considered "Waters of the US", and doing so would have an adverse effect on the environment.
Ideas we have considered:
1. Dig trench and install sump pumps - cheap but how effective?
2. Install sheet piling, dig trench and install sump pumps - expensive
3. Install wells - expensive, but how effective?
4. Launch the gabions into a wet trench with crane - expensive, difficult?
5. Install sheet pile cutoff at the toe and no excavation - not environmentally friendly
This is a planning study at this point, and I would appreciate any input on cost, feasibility, etc.





RE: levee construction
A wet excavation will be the cheapest, but may be difficult because of the silts clouding the water and obstructing the contractor's / inspector's view of the work in progress. Not to mention the risk of triggering a slope failure.
Sump pumps are pretty risky to me - I've been burned by this approach. Go this route only if you have a bonded, experienced contractor willing to do the job on a performance basis (i.e. he will dewater to a certain elevation for a certain period of time.)
Permanent sheet piling will work, but expensive. Temporary sheet piling can be risky - sheets can damage gabions during extraction.
RE: levee construction
is getting a suitable even base in a slurry type river bottom. Possible solution is to use fabric formwork as your scour toe or base and partly up or all the way up the bank and then cover with gabions or just use sufficiently thick concrete mattress. Fabric formwork will eliminate any water pumping requirements.
RE: levee construction
RE: levee construction
Let us know how you make out.
RE: levee construction
Installing gabion linings into wet channels is done on a routine basis. The type of equipment available will dictate the amount of gabion installed per cycle - large capacity cranes will be expensive, but allow you to install more m2 per cycle. Smaller cranes are cheaper, but not as productive. Gabion/Reno mattresses are assembled and prefilled in the dry and placed into position.
Because the gabions are a flexible structure, they will conform to the subgrade.
Depending upon the depth of water, divers are also frequently part of the equation.
Contact the Technical Department at Maccaferri, Inc. They will be able to provide you with additional design assistance.