# Building bridges in swampy conditions



## YELLA-ONE (Dec 7, 2009)

So I am building a trail for someone in their backyard . But I have a dilemma......I have a swampy area that I have to build elevated trails (skinnies) on , and quite a lot of them too , about 500' . What I need to know is can I still drop posts in to the ground to secure the structure or should I use another method ie. cribbing with rocks or something like that .

The home owner say that by about mid season the area is dry , but thats not what I am worried about , I am more worried about the beginning of the season when everything is soft and malleable . I don't want him to be going trough a high speed berm to have the structure shift on him or any one of his friends.......heres some pictures of part of the area , probably the worst of it

Each of those flags represents a post (rough cedar posts) , and in total there are going to be over 100 of them for the primary line alone


















This is what the area is like in detail , if you step in that you will sink past your ankles










I'm used to building in dry conditions and need your help 

Paul


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## Trail Ninja (Sep 25, 2008)

Your wood is going to rot eventually no matter what you use. Red cedar will last the longest. Stone is good if the muck isn't too deep. Steel posts with "feet" will work too. Dig them in and fill with rock to hold them still.

I have built "floating" bridges with red cedar over similar stuff that's still good 10 years later. I used 18" to 24" diameter logs about 6' long laid across the trail right on the surface and stringers in top of that and then the decking. Really stable but hard to build it high. 

The softer your muck, the longer the cross logs should be. There is a point where the bridge will actually float on water. Then it's a dock. If that happens, sink a few posts right through a space in the decking to hold the whole thing in place.

The simple explanation for bermed corners in a system like this is, use different diameter stringers.

Oh, I should mention that we don't have a winter freeze here. The floating dock system might heave during freeze up and need some tweaking in spring.


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## Fletcher-Love (Nov 14, 2009)

I was going to suggest something very similar to what Trail Ninja just posted . I built a wood starting ramp in the same kind of environment and used treated lumber (instead of logs) I scrounged from a deck demo. I made the main supports lie flat so they essentially floated in the mud and then cross braced off of them to support the structure. I tied the whole thing to a very large boulder that was not going anywhere.... just in case.


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## Megashnauzer (Nov 2, 2005)

you might try driving piles in the ground with a pile driver. someone told me that you could rent an air powered pile driver but they may have been f.o.s. drive them until they don't go in anymore.


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## woodway (Dec 27, 2005)

We built a ladder over a similiar type of area - swampy and wet in the winter, dry in the summer. I attached a photo of the trail line in mid-winter and a couple of photos showing our construction techniques. We used concrete pier blocks to elevate the wood off the ground. All the stringers were salvaged from around the bridge and the bark was peeled off them so that they will last longer. This bridge is about 135' long. For 500' the pier block technique is probably not a solution for you, but you could potentially use them in strategic spots.


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## Trail Ninja (Sep 25, 2008)

Those deck blocks work pretty well. How old is that trail now and has it sunk much?

I tried that once years ago and it held up fine about 2 years and then one day (well more like a couple of weeks) the blocks just sank for no good reason. I didn't use steel ties so I lost the blocks. That's one place I have a "floating" log bridge now. It's a spooky swamp. When I first built the trail, the ground was solid enough that I figured deck blocks were OK and now you can push a 6" diameter pole 12' into the muck by hand.


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## woodway (Dec 27, 2005)

The bridge has been in place for 1.5 years. No settling so far. The galvanized brackets have a bolt on them so that if the do settle you can raise the height of the bracket.

I should mention that we dug holes for the blocks to solid ground. Where things were mushy, and solid ground was not a few inches down, we dug down deep till we hit a solid layer of earth, filled the hole with rocks and then dumped quickcrete into the holes and set the pier blocks on top.

Those pier blocks are sure a pain to haul in though...


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## Trail Ninja (Sep 25, 2008)

Much better than my idea of just laying them on the ground until the swamp came back to life and swallowed them whole.:madman:


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## YELLA-ONE (Dec 7, 2009)

Would posts two feet in the ground with with gravel and "L" bar hammered in on an angle and nailed across the posts work to stabilize it ? That detail shot is just the worst area the rest of it is just a little water logged , and I got to be honest , he isn't looking for "permanent" structures , he might want to have them moved around a bit later on in the not so distant future 

Would that work ? 




Paul


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## YELLA-ONE (Dec 7, 2009)

Is there a way to roughen up dimensional cedar lumber to add grip for decking ? I.E take a wire wheel mounted to a drill and "grind" away at the surface , would something like that work ? 



Paul


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## woodway (Dec 27, 2005)

YELLA-ONE said:


> Is there a way to roughen up dimensional cedar lumber to add grip for decking ? I.E take a wire wheel mounted to a drill and "grind" away at the surface , would something like that work ?
> Paul


Just take the tip of a chainsaw and crosshatch it. Take a look at the log we split and used as an entry filter to the ladder. We used a chainsaw to carve grooves into the wood to give wheels traction.


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## Trail Ninja (Sep 25, 2008)

YELLA-ONE said:


> Would posts two feet in the ground with with gravel and "L" bar hammered in on an angle and nailed across the posts work to stabilize it ?


"L" bar hammered into the ground and then nailed across both posts? In an "X" configuration?

It would probably make the structure solid but the stability is going to depend on if you have your posts & "L" bar in something solid. If not, you could get uneven settling.

If you can dig to solid ground and fill with rocks, you'll probably be fine. If it starts to loosen up on you after a couple of years you get to rebuild and change the line. Not a bad idea for a small trail in a yard. The trails in my yard change every few weeks.

If you don't have a chainsaw to cross-hatch the dimension decking, you can rough it up with a hatchet.


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## YELLA-ONE (Dec 7, 2009)

So after taking a week off the swamp section is dry as a bone...........time to dig post holes  




Paul


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## YELLA-ONE (Dec 7, 2009)

90X 4"x4"x8' 
100X 2"x6"x8'
200X 2"x4"x8' 
Have arrived and the shitty part is that they all had to be brought down a VERY large hill by hand ! I have already started putting in the posts.....139 of the suckers are going to be sunk in the ground with gravel compacted around them . Lots of work ahead of me , but that should be easier now that I have hired someone to help 

Pictures to follow soon 




Paul


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## YELLA-ONE (Dec 7, 2009)

Just thought I would give you guys an update on the build progress......its solid as a rock even after a really good rain , I will be reinforcing it all once I am done both lines though










































and of course the tools that made it happen 










More to come

Paul


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## fishbum (Aug 8, 2007)

We normally use screws for the decking as we've seen the nails pull out over time... how about those nails? They look coated? Sure would be a lot less work with that Paslode gun!!!


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## YELLA-ONE (Dec 7, 2009)

fishbum said:


> We normally use screws for the decking as we've seen the nails pull out over time... how about those nails? They look coated? Sure would be a lot less work with that Paslode gun!!!


Oh it made the world of difference for this job , it wouldn't have gone as fast as it did otherwise .
I would have screwed it , but in this case I didn't see the need for the extra cost and time considering its only going to be ridden by a handful of people . This build is entirely on private property in someones backyard in Toronto...........must be nice to have the land and the money !!

Just wait to see the next line , its going to be pretty crazy ! 

Paul


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## Trail Ninja (Sep 25, 2008)

That looks really good Yella. I was going to mention the cross bracing until I saw you already mentioned it.

I used to live in T.O. years ago. Approximately (don't give away any secrets) where is that?

Going to go down in the Don and fix that up next?


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## YELLA-ONE (Dec 7, 2009)

Trail Ninja said:


> That looks really good Yella. I was going to mention the cross bracing until I saw you already mentioned it.
> 
> I used to live in T.O. years ago. Approximately (don't give away any secrets) where is that?
> 
> Going to go down in the Don and fix that up next?


It's in the Bayview & Sheppard area .
After work everyday I am in the Don doing my old rogue building routine....working on the DJ's , making more pump track and doing maintenance . The Don has become my home away from home for the last 6 years . In a city this big you have to find a place of refuge to keep your sanity in check.....or insanity , as the case is most of the times 

Paul


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## Trail Ninja (Sep 25, 2008)

I left Hogtown in the mid 80's after 20 years there. I lived in the East End and the Beaches. The Don was such a cesspool then. It's great to see the turn around. I used to ride there but it was before "mountain biking".

One day I'll get back there to have a look around. Keep up the good work & if you ever get out to Vancouver Island...


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## Buffrider1 (Jan 21, 2014)

I know this thread is sort of old but I found this site searching for ways to build just such a bridge over my creek/brook behind the house so I can get some wood from over that side and X country ski over in the winter/ Mtn bike over etc ...
Anyway, I am dying to know how you made the decking. It looks like local wood. Do you have a huge log splitter?
The salvaged wood for hte stringers - were those green fresh trees you cut down or tree falls that were hung up and dry?


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## woodway (Dec 27, 2005)

If you are talking about the pics that I posted Buffrider1, the county parks department did not allow us to cut any living trees - everything was salvaged from inside the park. The stringers were all downed logs that we salvaged, carried to the bridge site and peeled. The decking was down Red Cedar logs that we bucked to length with chainsaws and hand split using wedges and axes and then moved the the bridge site in wheelbarrows. Lucky for us, we have a lot of Red Cedar here in the Northwest as it makes great decking that lasts a good long time. This bridge was built in 2009 and sees plenty of use. The only repairs so far have to been re-nail or replace a deck board here or there. We've replaced maybe 3 or 4 deck boards in the last five years.


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## Dave_schuldt (May 10, 2004)

Check out this one we built near Seattle. We had a big storm a few years before so the county got most of the wood from that. Also an old dock and what we could find in the area. Deck board milled with chain saw. This was built over 2 winters and is 600' long.
Grand Ridge Boardwalk - YouTube
There was some false starts and mind changing plus some rework but it got done.
Consistent management is every thing on some thing this big.


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