Wetland Bridge

[whistler]

I visitied this site occaisionally during the process of building my cabin and have always gotten great information from previous posters. So thanks much.

However, I am having difficulty finding information anywhere for my latest endeavor and I thought this would be a great place to start.

My property in northern Minnesota is bisected by a flowage that I would like to cross easily. Starting from the high, dry ground there is about 20 yards of floating bog, mostly Labrador Tea, grasses, and the occaisional stunted Black Spruce. Then there is about 10 yards of open water, roughly 6 feet deep in wet periods. After the water is another 30 yards of floating bog before reaching the high dry ground.

I've spoken with the various regulatory agencies and determined the best course of action would be a boardwalk/walkway utilizing pilings. I would like the structure to support an atv. I am looking at about six feet wide or so with high sides.

The lakebed near the mouth of this flowage is roughly 2 feet of detritus (rotted vegetation and such), 6-8 inches of sand, and then clay. I suspect the flowage is similar although I have not done any 'core' samples.

Also, there is no road access to this parcel except in winter when the lake freezes over.

I am wondering, first, is this in the right forum? Second, does anybody have any information or know where I can find more information about a project of this magnatude? I'm especially interested in learning about drivable piling materials.

Thanks for looking at this.

Pete

[Cole]

Yes this is in the right forum. I am looking for some info for u.

[Rich]

Piles aren't that difficult to do in most cases - your problem will be how do you get the pile driver to the area where they need to be without being stuck in the bog.
Floating barge maybe? I know they do this in river crossings - but not sure how it would work in your situation.

[Cole]

Piles aren't that difficult to do in most cases - your problem will be how do you get the pile driver to the area where they need to be without being stuck in the bog.
Floating barge maybe? I know they do this in river crossings - but not sure how it would work in your situation.


That is going to be your problem. Your best bet is to call a local boat dock building company.

[whistler]

Wow! You guys are fast.

Cole_21, thanks for the welcome. And I appreciate you taking the time to look for some resources.

Rich, since this will be a smallish boardwalk, would it be possible to go with metal posts, drive them by hand, and use connectors of some sort to increase the depth as needed -- similar to a sandpoint well?

Pete

[Cole]

Ok here is what I have come up with, if you build the bridge in sections you could easily make it maybe doing 20' at a time. I know that you can get a excavator mounted pile driver. But since your area is so wide, i think maybe a long reach excavator should be able to drive your pilings.

[whistler]

Piles aren't that difficult to do in most cases - your problem will be how do you get the pile driver to the area where they need to be without being stuck in the bog.
Floating barge maybe? I know they do this in river crossings - but not sure how it would work in your situation.


That is going to be your problem. Your best bet is to call a local boat dock building company.

Good call on this. There are a couple places by the cabin I could check with.

Pete

[Cole]

This is what we use.

http://www.hmc-us.com/hmcsp/movaxseries.html

[Cole]

:arrow:

[whistler]

Holy crap! That is huge.

I don't think the hassle of getting something like that into my boggy stream would go over so well.

Is there a way to do it on a much smaller scale? I'm not so much concerned about speed and efficiency as I am about minimizing cost. I've gotta think getting one of those bad boys over there would cost me several grand.

Pete

[Cole]

Yeah, actually you can do it on smaller scale and it would be perfect for your application. How deep do you want to drive them?

[whistler]

Whew!

As for how deep to put them, I don't know. I really know next to nothing about pilings except what they are used for.

I imagine that depth is determined by load, area of the bottom face, and substrate but I do not know how these things interrelate. Is there a rule of thumb to this?

A four wheeler, gear and my fat carcass would weigh about 1200 lbs. I'm thinking treated 2X8's 2' o.c. spanning 10' with treated 2X6's for decking. I would estimate that each 10' section would weigh about 400 lbs. A pair of pilings each 10 feet.

Looking at about 200 lbs per piling dead or 1000 live. Where does this leave me?



Pete

[Cole]

Im asking around for some more info, I got a one more question for you and it is a big one, How much are you willing to spend?

[Cole]

We have bridge engineer on the forum now so I will pm him for some more info.

[Rich]

We have bridge engineer on the forum now so I will pm him for some more info.

We do? :)

[Cole]

Yeah Rich, i sent you a pm the other day, or maybe I did i dont remember but his handle is digger.

[whistler]

I'm willing to spend what it takes.

Thanks much.



Pete

[Cole]

I'm willing to spend what it takes.

Thanks much.



Pete


We have this saved now, :lol:

Seriously though, let the engineer chime in here when he gets online, just I dont know when he is getting back online. I sent him a pm and a email so he should be on in the next couple of days.

[whistler]

Great!

I look forward to hearing from digger.

Pete

[Cole]

So let me get this right, 50yds is 150ft right? So u are looking at spanning 150'x 10'?

[mjpliv]

Pilings are usually driven to refusal. They go untill the equipment can't move them anymore.

I would use the barge method but you will have to winch it from one side to the next. This will also have the least amount of environmental impact. You will only disturb the surface vegetation.

[whistler]

I'm sorry I was a more than a little confusing with my dimensions.

I am looking to build something about 4 feet wide by 150 feet long. I was thinking about putting a pair of pilings every 10 feet along the 150' length of the bridge. This would allow me to build in 10 foot increments.

Pete

[whistler]

Pilings are usually driven to refusal. They go untill the equipment can't move them anymore.

What if that equipment is me, my back and a 12 lb. sledgehammer?

I would use the barge method but you will have to winch it from one side to the next. This will also have the least amount of environmental impact. You will only disturb the surface vegetation.

It seems that this would create trouble with the nature of the floating bog. The equipment, if not on a huge load-spreading platform, would sink easily into the bog and then we would really have a problem. I don't know that we could winch a barge and a piledriver up onto the bog without ripping it to shreds.


Pete

[mjpliv]

10-16 feet sounds realistic for regular dimensional lumber, more if you have some heavy timbers you can use

[mjpliv]

Then you would be driving some pretty light weight pilings. This could be done but I would do it as two legs on either side of the walkway tilting towords each other, connected at the top and braced above the water (in the shape of an "A". Then I would cross brace the two pairs together under the platform. This would give you a fairly stable platform if you only want to drive them by hand. But be prepared for it to move quite a bit in the winter if the bog freezes.

[Cole]

Ok i came up with a great idea but you pretty much have to know the depth of the water and the denisty of the soil underneath? You could build it in sections and set them in the bog with a crane or a excavator. Another thing you could do is dry dock the place you are going to drive piles in and work with the water around you. Which can be done fairly easy with a steel box built and set in the bog and pump the water out.


Her is the idea I was talking about with pre-fabbing the pile structure and setting them into place( that u have no clue how much it is going to settle and getting it level.) Just an idea.

Sorry for the drawing, i am away from the office and all I have to use is paint.

[Cole]

BTW- I am working on a suspension bridge too,

[digger]

Well i see some great advice and some nice pictures. A couple of suggestions, first in the bog areas (shit land) i would suggest to build out infront of yourself, like has been stated. ( Are there any environmental laws-or neighboors?) I would build in 10' sections. The piles i would use 6"x6" presure treated. dig as far as possible with a post hole digger then drive the piles the best u can with the biggest sledge u can handle, LOL. Maybe even incorporate the "A" fram detail of slanted piles conected at the tops.

The span over the water is the tricky part. Its to far to span, u may need a install support in the middle of the water area (telephone pole). In the past we have used telephone poles. You can use a 30' pole on each side, connect the top with 6x6's or a cut pole, then deck over that with 2" decking or some kind of scaffolding lumber. The center pier or support would also be telephone poles. This should carry small veh., jeeps,

To drive poles, we used a small backhoe and just smashed the pile with the buckett. If u can get a ATV maybe... you can get a small backhoe out there.

On onother note, I have seen in logging areas they drop 30" trees across a span and chain them together, yes they did build a rude abutement so it didnt wash away so easily, this would carry large logging trucks.

Another system to consider for the bog areas would be a floating mat system.

Good luck!
digger
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[Cole]

Great Ideas, Im glad u gave ur input.

[whistler]

You guys are awesome. Thanks for the help and information.

mjpliv and cole-Thanks for the info on bracing. I really hadn't thought of how to brace all this stuff together.

digger-thanks for the idea of telephone poles. We have a pole company nearby and perhaps I could get something worked out. If I am only looking to support 1500 lbs. would I really need center piers if I put in three telephone pole stringers? Or is it the case that the weight of the poles is about all they can handle? Or what about using web-style floor joists? Do they make them babies strong enough for the kind of load I am looking at? I could always space them 12" o.c. or closer if need be.

A couple of things I was thinking about regarding pilings. I think I could a backhoe onto the bog in the winter, but can you drive pilings (steel) through frozen ground? If I were to drive them, how would I connect sections together?

Alternatively, many people around here use auger-type post bottoms and screw their dock supports into the lakebed. Rather than driving pilings down could we screw them into place?

I assume because they are not sitting on 'anything' to distibute the weight they will continue to sink, correct? Are there some sort of expanding footings that might work for something like this?

Also, on the winter movement issue. Where does the movement come from? I imagine that I will get the pilings below the freeze line so frost heave shouldn't be an issue, should it? Is it more the case that the bog will shift and drag the pilings with it? Or is it the general sinking and settling of pilings sitting on a non bearing surface?

Thanks much for your continued help.

Pete

[whistler]

Are there any environmental laws...? Another system to consider for the bog areas would be a floating mat system.

As long as I keep it to a narrow width and use pilings environmental laws do not come into play. I think a floating mat system with courderoy would require permits and I would be severly restricted in what I can and cannot do.

Pete

[plunkinberry]

Sorry I'd missed this until now... but I'll add my two cents...

Since you only need to support around 1500 lbs; I'd look into driving 6" posts (like long fence poles). Specifically, I'd look into finding a farmer in the neighborhood (general area) with a four wheel drive tractor with a rear mounted, PTO or hydraulically driven pile driver used to set fence posts. These will drive a 6-inch diameter log into solid ground in several minutes; going into your bog should be easy. The four wheel drive would facilitate self extraction when necessary.

Crossing the actual water portion of the bog will be a greater challenge but again, could be accomplished during the winter. To facilitate driving through frozen ground, cut a point into one end of the post.

As for the floating mat, as long as its only a temporary thing, I don't think you should get much resistance.

[Cole]

Why not just wait till it freezes and bring some excavators in and dig that area out and run some piles into the ground? That looks like it would be the easiest solution.

[whistler]

Why not just wait till it freezes and bring some excavators in and dig that area out and run some piles into the ground? That looks like it would be the easiest solution.

I don't know if there is any easy solution :wink:

Pete

[Cole]

Why not just wait till it freezes and bring some excavators in and dig that area out and run some piles into the ground? That looks like it would be the easiest solution.

I don't know if there is any easy solution :wink:

Pete


Ur not lying. :D

[marx]

Whistler, Could the portion that is always in relatively deep water be bridged with floating sections of deck. Not the floating mat described earlier but sections of decking attached to something that floats and connected by some means.

So there'd be an approach on each side that's done with posts/pilings then the middle section/s are floating on old barrels , or large styrofoam chunks.

There's a wetlands park near where I live that uses this method, well sorta. There's an observation deck in the middle of a beaver pond. The walkway to that deck is on posts, the deck floats on plastic barrels. The connecting deck walkway is secured by short links of chain.

-m

[Cole]

Whistler, Could the portion that is always in relatively deep water be bridged with floating sections of deck. Not the floating mat described earlier but sections of decking attached to something that floats and connected by some means.

So there'd be an approach on each side that's done with posts/pilings then the middle section/s are floating on old barrels , or large styrofoam chunks.

There's a wetlands park near where I live that uses this method, well sorta. There's an observation deck in the middle of a beaver pond. The walkway to that deck is on posts, the deck floats on plastic barrels. The connecting deck walkway is secured by short links of chain.

-m

Great Idea that would probably work the best and probably be the cheapest.

[whistler]

Whistler, Could the portion that is always in relatively deep water be bridged with floating sections of deck. Not the floating mat described earlier but sections of decking attached to something that floats and connected by some means.

I just got ahold of 20 55 gallon drums for this express purpose. I think this will be the easiest part of the whole darn thing.

I did some test pilings (2" steel pile and a sledge hammer) and there appears to be quite a bit of clay clay/gravel in the bog bed. The biggest headache seems to be getting through the bog. Whew boy, what a mess of roots and decaying plants.

I appreciate all your help and advice. Unfortunately I cannot get started on the project yet this fall. I anticipate freeze up in about 10 days. I will probably have more questions about this come spring.

Pete

[Cole]

Right on, have fun.

[mjpliv]

Keep us in mind and let us know what happens.

[Cole]

Check this out if everything doesnt work.

http://www.aquabarrier.com/