How to build a foot bridge?

[Western]

Does anyone have any suggestions on how to build a walkway (footbridge) over muskeg or a wetland?

My in-laws have some land that is divided in half by a creek and they want to find a way to cross, initially by foot and then hopefully later with an ATV. The creek has beaver dams above and below the property so the stream isn't very deep. The open water is only about 3 yards across but about 20 yards from each bank is a floating grass mat.

We laid down some logs for now that spread a persons weight pretty easily but looking for ideas for a more sturdy and easily crossable bridge. My balance is tested staying on wet logs.

Would pounding pipe down work or would frost and ice destroy it each winter?

Thanks
Western

[Map Maker]

Screw piles.
I put a long one boardwalk in over a swamp and worked great.

Pounding a steel pipe might work. The frost might not grab it.

[Sooner]

Wait for freeze up, cut 4 larger trees to make the span, drag to the spot for a crossing and pull across the span. Build across the trees a wide wood deck. Will last a few years easy enough and "float" across the grass and muskeg so to speak.

We did this at a friends land who has a seasonal creek. Some years the water flows over, most under. A chainsaw levels where the boards need to be.

[pa_of_6]

Lay logs cross wise, side by side.
When you get to creek...use bigger logs or span the creek with logs and boards on top.

Then on the logs that are cross wise, put dirt on them and there you have a great crossing for cheap...only sweat labor

Really works great, but does take time putting them logs side by each.

[Don_Parsons]

Best swamp boots are large dried barn planks. 6" or 8" wide X 6' long.

They have pictures of them in the Florida Evergalds museum.

They are wider then cross country skis and work pretty good according to the swamp folks that used them.

They attached a lether loop over the top so your boots slip into them, then kick them off once you reach the hill side.

Some folks had 3 or 7 sets at each swamp depending where their cabin on stilts was located.

Im thinking those folks worried more about getting eaten by a Alligator other than drowning in the byeu.

Don

[Arty]

Get out your engineering notes and textbooks, your steel handbook, your bridge design case studies, and draw up a nice little bridge.

It sounds like a 50-meter span over a flood plain. The dams may or may not be 'maintained' as you expect over the next decades, and the creek might grow a lot wider than you expect. (Google 'Houston flooding')

I'd first get some geologics done (simple cores) on either side so you know what's underneath that you have to deal with. Clay and alluvial deposit, probably. I'd stay away from any kind of wooden flotation mats or corduroy because there's too much water involved to stabilize it easily, and because it would rot out pretty quick. Dumping big amounts of gravel down and putting a culvert is not cheap either. We're not looking for a road you could drive a tractor over.

Spancrete tables seem to top out at 46 feet, and I'd guess any precast beams would be way out of acceptable cost and weight range. Welded spans like Calgary's Bow bridge or Edmonton's Mayfair Park bridge would probably be in the millions too.

So maybe a cable suspension bridge would be best. A pair of screw pilings either side of the marsh, that can have short towers welded to them, and a couple of cable anchors of some sort a little further inland. Then do weight and caternary calculations to see what cable strength you need and otherwise follow up designs done on other structures over the years. That would be a totally cool project.

[dmcbride]

Make a floating bridge (dock) with barrels.

[Grizzly Adams]

Originally Posted by dmcbride

Make a floating bridge (dock) with barrels.

Easiest, cheapest solution.

Grizz

[hayseed]

Originally Posted by dmcbride

Make a floating bridge (dock) with barrels.

YEP.. why not.

Please don't do what Parsons suggests.

[bryanfewchuk]

an old flat deck semi trailor buy cheap at an auction

[kodiakken]

Originally Posted by bryanfewchuk

an old flat deck semi trailer buy cheap at an auction

I have seen a few of these. Makes so you can cross with a vehicle too.

[Sundancefisher]

Originally Posted by Grizzly Adams

Easiest, cheapest solution.

Grizz

Ditto

Muskeg can be very deep.

Otherwise buy an Argo.

[Don_Parsons]

Originally Posted by hayseed

YEP.. why not.

Please don't do what Parsons suggests.

LOL, don't use the sinking barn planks as they will only bog you down. Ha.

The better Evergald crossing system is 2 wide planks layed down on top of the swamp grass,,, watch for deer crossing as they seem to know were the crossing areas are. They would Criss cross the planks in a zig zag pattern.
https://www.pinterest.com/pin/290060032220412544/

Caution too the max my friend, don't cross swamps in the dark and buddy up incase things go south.

Swamps or bogs are not forgiving.
One does not want to experience getting bogged down.

Don

[Arty]

Originally Posted by Arty

[...] a cable suspension bridge would be best. [...]

Definitely the best solution. Wished I thought of it myself.

Following is the cheaper, refined version:

You get two old telephone poles, one for each side of the marsh/creek. Drill a hole in the ground 6 feet deep or better for each with a power auger, a little wider than the pole. Dump a foot of gravel in the bottom and tamp it down real good. Put in the pole, and surround it in the hole with concrete. Let cure. That will support all net vertical load exerted down by the cable.

Put 3 guide wires around each pole 130 degrees apart, to counteract all lateral and longitudinal forces due to wind or various unexpected environmentals. Those are just for non-operational forces; have nothing to do with the main cables. Those guide anchors & wires are just like the kind used for power distribution poles, nothing new.

Drill a lateral hole across each pole, up where the caternary should attach according to the calculations. Put a 1-inch diameter piece of rebar or better grade steel rod through each pole, and put 2 heavy steel sheaves around each, with lock-collars close to the pole. That's to let the movement of the cable from heat expansion work back and forth. Net thermal effect will only be to lift/drop the cable height a few inches over the course of the year.

Drape two weight-bearing cables over the 4 sheaves, of the proper calculated length and guage, and attach the end of each cable to a double-redundant cable anchor in the ground, just like the type used for power transmission poles but heaviest gauge. That's your catenary backbone. https://en.wikipedia.org/wiki/Catenary

Then attach a light decking. Every meter, attach and drop a thin cable down from each caternary cable to deck height. Attach 2-meter long square aluminum spars to the ends of the drop-cables, to serve a boomsticks. Attach cross-decking of a light strong cheap material. Each of those 2-meter long by 1-foot wide suspended islands is snubbed to the next with cheap nylon rope. The islands' suspension is biased slightly higher as you go towards the middle of the bridge, so the hot steel cables in the middle of summer at their longest length will produce a flat horizontal decking from one end to the other.

Fasten a length of cheap 3/8" nylon rope at each side to each drop-wire, from one end to the other, 5 feet high, as a hand rail. Fill in at the bottom with light snow fence or similar, fastened to each island and to the handrail rope.

Note that the heavier the decking gets, the heavier the main and drop cables you'll need, which will increase cost and difficulty of installation. If the deck gets a little active, it could be snubbed to each bank with 3/8" nylon rope.

That's it.

[Smokinyotes]

Break the dam below and above where you want to build the bridge. Shoot or trap all the beaver. After a month when the area has dried out build your bridge across the 3 yard creek.

[KinAlberta]

We have a similar situation. About 30 yrs ago a friend welded up a bunch of surplus channel steel into a bridge. Long pieces of channel steel was welded into square tubes for the beams and channel used for the decking (with 4 long pieces of surplus drill tubing steel rising from either side of either end up to a centre cross member that looks like an upside down "U" about 7' high also made of drill stem.) welded on skid tips to skid it into place in the winter about 30 yrs ago.

It was just set on the banks of the creek. Only problems are that; one, it settled into the bank over time (I'll jack it and put wider pads under it up soon) and a beaver dam put the beams under water. So we'll try a DIY beaver dam leveling device in soon.

Anyway, the bridge has worked fantastically well all these years. It's maybe about 6'x50'.

[Norwest Alta]

Originally Posted by bryanfewchuk

an old flat deck semi trailor buy cheap at an auction

This. Works good

[dantheman93]

pallets connected with beams

[Big Grey Wolf]

Soooner is only practicle guy. Large logs pulled across then planks on top. We build dozens of bridges on trapline using this technique. If you are near green zone you can borrow/cut the queens logs from your favorite logging companies lease, they owe you a few.

[Sooner]

Originally Posted by Big Grey Wolf

Soooner is only practicle guy. Large logs pulled across then planks on top. We build dozens of bridges on trapline using this technique. If you are near green zone you can borrow/cut the queens logs from your favorite logging companies lease, they owe you a few.

Just copying what I have seen done on many cut lines and trapper trails I have quaded while hunting or sledded over

[KinAlberta]

We've done a few things with logs and untreated wood. Quick and cheap but at some point we are dealing with rot and adding another task to a full schedule.

Like our use of untreated or non-cedar deck boards, we've been there and done that. Two or three years in, a board rots then we'd toss a temporary piece of plywood over the rot then trip over it for a decade or two cursing our cheapness and laziness at not replacing this board, and the next one. And the next one... as more and more plywood patches showed up. Then there's the added risk of hidden rot that can ruin your day.

It's like using cheap shingles, cheap paint, cheap whatever. Before you know it you're doing the job again, forever pushing fun things aside to deal with failures.

:-)

[Big Grey Wolf]

If you use heavy pine planking the bridge will usually wash out by a major flood long before the planks rott. Always leave space between each plank so they dry out well after each rain storm.

[bubba300]

I used to work at a oil battery in NWT we used 3"x12"x20' rough cut pine for quad bridges,we used logs,pellets or 3x12 as cross boards then layed the 3x12 on top and spiked them together sometimes in the really wet area's we would run the 3x12's side by side just to give you more room to stay on the bridge.Usally they required some fixing up in the spring and through out the summer but worked pretty well.

[Arty]

It looks like a few people are missing the actual width which has to be spanned, and nature of the banks & supports.

There's approx 150 feet to be crossed, maybe 50 meters or more from soft dirt bank to soft dirt bank. 10 feet is easy. 50 feet might be a bit of a problem, but doable with cheaper materials. 150 feet or more is exponentially more difficult and requires some specialized structure.

If you crane or winch a heavy 20 or 50 foot device of any kind onto a creek & marsh or lake you'll eventually just get a submerged structure. I've used lots of log bridges in Alberta, even helped build part of one. But those all needed solid end-supports, typically of log caissons filled with stone, and didn't span 150 feet. I've never heard of a 160 foot spruce or local fir which can support itself and a vehicle along its entire length while laying in dirty water. A 'floating grass mat' to me means water underneath.

You can certainly walk up and down a floating fir log raft, but those are meant for temporary cheap transport of logs down the coast to a mill. Over time they get waterlogged and sink. Some people have even set up companies to dive down and salvage logs from staging areas and transport channels to sell to mills, because there's so many of them which have sunk over the years.

For light foot traffic over 150 feet between 'dry' land, I still think a couple cables would be optimal.
https://www.theguardian.com/travel/2...charles-kuonen

[Map Maker]

Originally Posted by KinAlberta

We've done a few things with logs and untreated wood. Quick and cheap but at some point we are dealing with rot and adding another task to a full schedule.


It's like using cheap shingles, cheap paint, cheap whatever. Before you know it you're doing the job again, forever pushing fun things aside to deal with failures.

:-)

Yep,
do it once, do it right.

The one i did three years ago takes alot of atv traffic and its still straight as an arrow.

I always get compliments on it.

[Western]

Wow, some stellar ideas. Some a bit more involved but would certainly secure access to the other side no problem.

We thought of dragging full trees across this winter and that might be the first step as we plan this a bit better. I also thought I should probably clarify my number a bit better and based on google earth the total distance would be 30-40m until you his soild(ish) soil. The floating grass mat is probably 10-15 m.

It is a big beaver flat and marsh so draining a few dams might be in order. Hate to seem them go as lots of ducks and geese use them and its nice to have them around.

Does anyone know if these sorts of things need to be approved by someone? It is a named creek so I would hate to screw pilings in or cables then have someone come and take to down.

[Big Grey Wolf]

I suggest you walk up and down the stream and pick the shortest span, least amount of work and material! If you want to traverse a swamp suggest rethink the project.

[MathewsArcher]

Originally Posted by Western

Wow, some stellar ideas. Some a bit more involved but would certainly secure access to the other side no problem.

We thought of dragging full trees across this winter and that might be the first step as we plan this a bit better. I also thought I should probably clarify my number a bit better and based on google earth the total distance would be 30-40m until you his soild(ish) soil. The floating grass mat is probably 10-15 m.

It is a big beaver flat and marsh so draining a few dams might be in order. Hate to seem them go as lots of ducks and geese use them and its nice to have them around.

Does anyone know if these sorts of things need to be approved by someone? It is a named creek so I would hate to screw pilings in or cables then have someone come and take to down.

http://www.qp.alberta.ca/documents/codes/CROSSING.PDF

[Don_Parsons]

You might want to contact your MD or County Rep to make sure they are in the loop, just being nabourly and on the up and up with them.

Our county Rep was good about us using old scrap trailer flat decks as we run cattle across them to keep them out of the creeks as much as possible.

2 options we had on our span was bank to bank support, or Friction pilings that hold the center sections of the trialers. 115 foot span.

The friction pilings did not hit hard earth down bellow since there isn't anything down there but goup,, so the friction around the piling is stead-fast by the pressure of the Muskeg around the outer surface of each piling.

We did 8 pilings on the first bridge that worked ok,,, 12 on the next as its much stronger.

This is for 11 to 1800 lb cattle or our 10 ton tractor when crossing.

The pilings are firm in the Muskeg as the top part of the stagg moves when the frost comes out of the ground in the spring,,, but the friction pilings are 30 to 40' deep as they aren't going anywhere.

No big deal if they do since the deck is free floating on the cross beams.

Just like a engineered bridge that allows for expansion and contraction with changing weather patterns.

Friction pilings are easy to do as our big track hoe had them in place in a few hours.

We put them in during the winter since the ground bellow is never frozen with running water.

Don

[Western]

How do you place friction pilings?


These are great suggestions. I suspect the county or gov't will have an issue with a flat bed trailer in the creek. Not sure what it is classified as yet. Swamp or fen or creek. Will have to call the folks at environ and parks.