Bog Bridges?

[Kevin Rooney]

A bit off topic, but ... I had an opportunity to hike in Ireland earlier this year, which as most know is a very damp country, with lots of highland boggy areas. Many of the bog bridges were old railroad ties, and often found them covered with 1/2" wire mesh, sometimes called hardware cloth. It was the best method I've every seen of reducing the slipperiness of a bog bridge. The cross-hatching you often see is an good method also, but not nearly as good as the hardware cloth.

 

[una_dogger]

A bit off topic, but ... I had an opportunity to hike in Ireland earlier this year, which as most know is a very damp country, with lots of highland boggy areas. Many of the bog bridges were old railroad ties, and often found them covered with 1/2" wire mesh, sometimes called hardware cloth. It was the best method I've every seen of reducing the slipperiness of a bog bridge. The cross-hatching you often see is an good method also, but not nearly as good as the hardware cloth.

The big bridges at Pondicherry are all wrapped this way ;/)

 

[MichaelJ]

Chicken wire works well, too. I've walked some bog bridges with that on it. I'm sure the risk is that over time as it ages, if enough wires break it could peel up, but if you have to build your bog bridge on an angle, it's a necessity IMHO.

 

[RoySwkr]

- second, largish stepstones set in cone-shaped holes are more permanent and need less building and upkeep than turnpike, which allows the walker to not watch their feet, unlike the rest of our trails. Turnpike is miniature road, and not usual on New England hiking trails.
...
The problem here is that for this to work to specs you need a large supply of small rocks and another of gravel....
If I was not assured of a good supply of gravel (rocks are seldom lacking),
then bog bridges are faster and easier than turnpike.

I disagree with the first part - walking on a dirt path (turnpike) is more like most trails (and more natural) than hopping stones or walking logs, which may be why some people here don't know what it means even though they've probably walked on it

There is no doubt that turnpiking to FS specs is immensely difficult and time-consuming, although it will outlast the stepping stones which keep sinking in the mud and the bog bridges which rot out

Since I do most trail work by myself, I can't safely move rocks big enough for steppingstones even if I could find them, and the same goes for large walking logs. Instead I once used what might be called poor man's turnpike:
* Use logs as big as you can conveniently handle along the sides butting ends as necessary
* Toss whatever small rocks are handy into the middle
* Toss the dirt from digging the side ditches into the middle

The side ditches will reduce the moisture content in the middle and the rocks will give it some firmness, I don't see how the soil would sink away leaving slippery rocks as in my experience it is the rocks that sink and need to be replaced

I read about this in some book, it's similar to the dredge and fill once done by Florida developers

 

[Mohamed Ellozy]

The big bridges at Pondicherry are all wrapped this way ;/)

A bog bridge in the Pondicherry reserve:

 

[Kevin Rooney]

The big bridges at Pondicherry are all wrapped this way ;/)

Nope, it's hardware cloth, not chicken wire. Big difference. Much more traction in hardware cloth as there's more wire per square inch, and the wire is thicker. Your boot never comes in contact with wood if hardware cloth is used. Not so with chicken wire.

Having said that, it's good to know that wire is starting be used in the Whites. It's a start. And chicken wire is generally much cheaper than hardware cloth as the wire is twisted, not welded.

 

[una_dogger]

The one negative I can think of is the shoulder season when you could potentially snag a microspike in the chicken wire or hardware cloth (thanks for clarifying the difference in materials, Kevin ). That could be a real downer.

 

[sierra]

Personally I do not like the use of any wire and hope it does not catch on. The main reason is, it will not hold up and become a snagging epic unless maintained on a regular basis, crampons will tear that wire to death. I like the logs a-natural, a little slippery maybe but they do not require upkeep once set for last many years as is, but thats just me.

 

[TCD]

My personal preference would be for prefab pressure treated bog bridges. Go in, measure the site. Come out, design and prefab the bridge with power tools, out of solid "lasts forever" pressure treated lumber. Predrill all bolt holes, etc. Carry in the pieces and assemble quickly and easily. You won't have to build it again for 50+ years.

I say this because the reality is that trail maintenance resources are getting more and more scarce. We don't have the resources to build stuff that's going to rot in 10 years. And we might as well build it right, with solid plans and power tools, so we don't get "leg breaker" gaps, split and failed wood, etc.

It doesn't bother me a bit to see a prefab PT bridge in the woods. A manmade bridge is a manmade bridge, and the trail is manmade anyway. If I don't want to see it, I'll bushwhack.

 

[DougPaul]

My personal preference would be for prefab pressure treated bog bridges. Go in, measure the site. Come out, design and prefab the bridge with power tools, out of solid "lasts forever" pressure treated lumber. Predrill all bolt holes, etc. Carry in the pieces and assemble quickly and easily. You won't have to build it again for 50+ years.

Some issues:
* I believe some forms of pressure treatment leach poisonous chemicals.
* Bog bridges are often built from local wood--carrying in prefab bridges may be harder than using local wood.

Doug

 

[TCD]

Both true. Thanks. I have thought about this a bit.

Not too worried about the chemicals - modern PT lumber is better in that regard than the old CCK lumber; and bog bridges are such a small footprint that the effects are insignificant. The ideal option, certainly, is to use Trex or other composite deck material; but it's more expensive than PT. If we can afford it, great.

Yes, prefab stuff would be easiest close to the road. Not too hard to truck in the individual pieces. For remote sites, I'd like to see the material choppered in. It's been mentioned here that SAR choppers are often looking for training missions. Lowering in a bunch of materials via a power winch would fit the bill. One solid chopper day could lower in all the materials our crews could assemble in a summer of work.

Certainly hybrid structures are an option. Big, long, local logs for the runners; short, light, predrilled trex pieces for the decking would be a good option.

 

[DougPaul]

Not too worried about the chemicals - modern PT lumber is better in that regard than the old CCK lumber; and bog bridges are such a small footprint that the effects are insignificant.

The leachant is presumably acceptable in developed areas, natural areas might be more sensitive. (I don't know--the ecology is different and could be more sensitive.)

Yes, prefab stuff would be easiest close to the road. Not too hard to truck in the individual pieces. For remote sites, I'd like to see the material choppered in. It's been mentioned here that SAR choppers are often looking for training missions. Lowering in a bunch of materials via a power winch would fit the bill. One solid chopper day could lower in all the materials our crews could assemble in a summer of work.

Choppers are extremely expensive. The ones with higher load capacities are even more expensive...

Doug

 

[Stash]

I agree on the concerns with attaching wire mesh for traction. I'd expect it to become a bit of a hazard when (not if) it gets torn up from crampons and such. A slipping hazard preventer becomes a tripping hazard. The sharp wire ends would also be a bit of a problem for dogs or other animals' paws. Even one wire broken and pointing up is a potential cut in a paw.

The bridges are going to be slippery no matter. Just as many rocks get. It's part of hiking. I ended up on my large pack like a turtle up side down with a slip just after taking this picture of what I see as very well constructed bridges in the Carters.

I find the best thing to do is to slow down on the bridges or anywhere there's potential to slip. It reduces butt bruising and gives you a chance to see more of what you're out there to see!

 

[Creag Nan Drochaid]

Real good work

The bog bridges Stash photographed appear to be by the AMC to USFS guidelines. Stringers are 3x8x8' roughsawn tamarack, helicoptered to near the jobsite. Sills are local fir or spruce, debarked and about 4' long.
The stringers are custom sawn for the AMC or the USFS, since 3" is also the depth of their bridge decks. Very helpful if you can get it, because mills usually saw to 2" thick. Bog bridges made of that require a third sill under the middle, or a cleat toenailed under the middle, if they are not to be uncomfortably springy.

 

[sierra]

I agree on the concerns with attaching wire mesh for traction. I'd expect it to become a bit of a hazard when (not if) it gets torn up from crampons and such. A slipping hazard preventer becomes a tripping hazard. The sharp wire ends would also be a bit of a problem for dogs or other animals' paws. Even one wire broken and pointing up is a potential cut in a paw.

The bridges are going to be slippery no matter. Just as many rocks get. It's part of hiking. I ended up on my large pack like a turtle up side down with a slip just after taking this picture of what I see as very well constructed bridges in the Carters.

I find the best thing to do is to slow down on the bridges or anywhere there's potential to slip. It reduces butt bruising and gives you a chance to see more of what you're out there to see!

Sweet!!!! those log bridges have "Digger" written all over them. How about the de-barked log waterbars? How many out there have got the middle part of thier boot set just right and road them for a few seconds before being pitched off the end?

 

[Stan]

... preference would be for prefab pressure treated bog bridges ...

This would indeed be a very practical solution once any leaching problems are licked but it begs a philosophical issue to preserve the backcountry in a manner that beckons one's own sensibilities and wise uses of the resources at hand.

The fact that we can build anything anywhere to any specification we desire does not mean we should do it.

It would sound far fetched to next elevate the bog bridge a bit, maybe use concrete for even better durability and put in a couple blinds and maybe a helicopter pad to assure universal access but this is the same slow creeping intrusion into the wild that occurs unnoticed until viewed across generations rather than years.

As for the design of the puncheons themselves and use of hardware wire and the like, I say there is no universal answer. Let the local trail builders and maintainers do what fits their experience, skills and resources and let's be grateful for whatever is there ... sort of like counting your blessings instead of your faults.