Building a Log Bridge

[Kidd]

Folks, I need to build a bridge spanning roughly 30ft over a creek.  In the spring the Creek typically overflows it's banks so there will/may be a period where the bridge is under water. I plan on using logs I cut on the property as the support beams and putting decking on top of that.  My question: how do I determine the size of the logs needed to support the weight.  I want the bridge to support an ATV and a trailer where max poundage would not exceed 700 - 800 pounds.

Thanks in advance.

[Walleyehooker]

Don't know for sure but my guess would be 8 inch plus diameter on logs spanning 30 feet. Ideally I would look for a couple used telephone poles.

[leech~~]

Just watch Alaska: The Last Frontier bridge building video!

[Kidd]

I've thought of using telephone poles, and still might, the problem is getting the poles to the location.  It's a couple hundred yards from the road to where the bridge will be built and I cannot get any heavy equipment down there.  Whereas I can cut trees much closer making it easier to move them into place.

Thanks for the feedback.

39 minutes ago, leech~~ said:

Just watch Alaska: The Last Frontier bridge building video!

Seems every video I watch they're using equipment I cannot get to my location

Edited January 19, 2016 by Kidd
seems you can't use the word s i t e

[leechlake]

it will depend on the specie of log but 8 inches would suffice for sure whether you used aspen/pine vs birch/ash.  Peel the logs so they don't rot as fast.  

[Tom7227]

Another thing you have to think about is how to keep it in place when the water is high.  My cousin built one on his land and it floated away the next spring.  I can't remember how he solved that but it is something you must consider.

[leechlake]

I think if you dug some vertical logs into the ground you could fix the bridge to it.  Depending on the current strength would tell you how deep they need to be.  

[delcecchi]

6 minutes ago, leechlake said:

I think if you dug some vertical logs into the ground you could fix the bridge to it.  Depending on the current strength would tell you how deep they need to be.  

gack.  How the heck deep would they have to be?      If there is a significant current, the bridge is gone unless maybe big chunks of concrete. 

This might be a case for a bridge that can easily be replaced if high water takes it away.

Edited January 20, 2016 by delcecchi

[Kidd]

At the moment I'm thinking of building concrete footings on both sides of the creek and anchoring a vertical log to the footings and pounding spikes into the vertical log through the main support logs.  Hoping that will withstand the spring thaw or any major rainfalls. 

[leech~~]

5 hours ago, Kidd said:

I've thought of using telephone poles, and still might, the problem is getting the poles to the location.  It's a couple hundred yards from the road to where the bridge will be built and I cannot get any heavy equipment down there.  Whereas I can cut trees much closer making it easier to move them into place.

Thanks for the feedback.

Seems every video I watch they're using equipment I cannot get to my location

4 wheelers ropes and chain saw?

2 hours ago, Kidd said:

At the moment I'm thinking of building concrete footings on both sides of the creek and anchoring a vertical log to the footings and pounding spikes into the vertical log through the main support logs.  Hoping that will withstand the spring thaw or any major rainfalls.

Now your talking about something the DNR may want to talk to you about even on your own land. Makes no never mind to me but it sure would suk if they found out and made you rip it all out?

[leechlake]

I envisioned the normal creek in our area not a torrent river in Colorado.

[BLACKJACK]

I would seriously consider some treated 8x8's, or cut down some hardwoods, something thats not going to rot out in 10 years.  If its for a a 4 wheeler, use that to drag them there.

 

Good luck.

[dairyman]

GO WITH THE TELEPHONE POLES IF YOU CAN------------------i WAS ABLE TO DRAG 30 FOOTERS---NO SWEAT.THAT WAS WITH A 400 EXPLORER

Edited January 20, 2016 by dairyman

[SwivelDigger]

We built a mat bridge across a river in Rochester for my work. They were 20 feet long and 1 foot thick and we were able to walk a D6 size Dozer and a medium sized excavator across them no problem so I think 8 inch would be plenty for a wheeler/ trailer. I would go with telephone poles if at all possible as they would probably last longer. Or stop at a local sawmill and see if you could get white oak. The better you build it obviously the longer it will last

[Cheers]

So if all you need to support is an atv what about a floating dock and cable system and use it as a ferry ? No issues with environmental  folks or flooding

[Macgyver55]

 I would seriously consider what "leech" said!

 There are a lot of rules about this type of thing  that you wouldn't expect. 

   The following is just a small part of what is on the DNR page  about water crossings etc. 

[Kidd]

Wow, lot's of great ideas and information.  I can't thank all of you enough.

As far as using telephone poles:  I will be checking that out and hopefully be able to find a couple.  The location needs work as there is a small wetland between the road and the bridge location.  I'll be constructing some sort of boardwalk or something to get the ATV across that so that does pose a small problem but easily remedied.  

As far as the DNR rules: The reason I'm making a 30ft span is to eliminate the need for placing any support logs in the stream bed.  This seems to be the biggest hang up as far as the DNR is concerned.  We put a small bridge across a Trout stream, about a 15ft'er, in the Grand Marais area and the DNR gave us their blessing as long as we didn't disturb the stream bed.  I'm hoping this bridge will be the same.

I guess I'll drop the concrete footings idea and use buried End Sills.

The following a picture of what I'm thinking:

  

[Tom7227]

Those DNR rules are very specific and maybe hard to meet.  If you have to have a 3 foot clearance from the water it would seem to rule out an awful lot of areas unless you arch the bridge somehow.  Kidd, does your topography allow for it?  I'm not sure that your drawing would comply because it looks like you are excavating to put the devices in at the ends to anchor it.  I'm not sure what it means to require removal of the bridge for maintenance.  You can remove just about anything if you have the proper equipment, but renting a big helicopter to lift it could be a bit troublesome and expensive.

Keep us informed on what you end up with as I see this as a thread that a lot of folks will read for future guidance.

[Kidd]

1 minute ago, Tom7227 said:

Those DNR rules are very specific and maybe hard to meet.  If you have to have a 3 foot clearance from the water it would seem to rule out an awful lot of areas unless you arch the bridge somehow.  Kidd, does your topography allow for it?  I'm not sure that your drawing would comply because it looks like you are excavating to put the devices in at the ends to anchor it.  I'm not sure what it means to require removal of the bridge for maintenance.  You can remove just about anything if you have the proper equipment, but renting a big helicopter to lift it could be a bit troublesome and expensive.

Keep us informed on what you end up with as I see this as a thread that a lot of folks will read for future guidance.

The 3ft rule is not an issue as the banks are 5 - 6 ft over normal flow conditions.  The rule having me scratch my head is the one end swing away rule.   

[leech~~]

1 hour ago, Kidd said:

Wow, lot's of great ideas and information.  I can't thank all of you enough.

As far as using telephone poles:  I will be checking that out and hopefully be able to find a couple.  The location needs work as there is a small wetland between the road and the bridge location.  I'll be constructing some sort of boardwalk or something to get the ATV across that so that does pose a small problem but easily remedied.  

As far as the DNR rules: The reason I'm making a 30ft span is to eliminate the need for placing any support logs in the stream bed.  This seems to be the biggest hang up as far as the DNR is concerned.  We put a small bridge across a Trout stream, about a 15ft'er, in the Grand Marais area and the DNR gave us their blessing as long as we didn't disturb the stream bed.  I'm hoping this bridge will be the same.

I guess I'll drop the concrete footings idea and use buried End Sills.

The following a picture of what I'm thinking:

  

If you go with  tele poles there is one place I think between Clear Lake and St Cloud on hwy 10 that sells them.

Edited January 20, 2016 by leech~~

[BLACKJACK]

1 hour ago, leech~~ said:

1 hour ago, leech~~ said:

If you go with  tele poles there is one place I think between Clear Lake and St Cloud on hwy 10 that sells them.

If you go with  tele poles there is one place I think between Clear Lake and St Cloud on hwy 10 that sells them.

I wonder about the telephone poles and how long they'd last if they're actually touching the ground and getting wet and staying wet??  They're fine if they're upright, the part in the ground is treated, the part above the ground dries out, not so sure about having it at ground contact all the time....

 

And how do you get a 50 foot pole to the page from hwy 10??  Will they deliver??

[leech~~]

2 minutes ago, BLACKJACK said:

I wonder about the telephone poles and how long they'd last if they're actually touching the ground and getting wet and staying wet??  They're fine if they're upright, the part in the ground is treated, the part above the ground dries out, not so sure about having it at ground contact all the time....

 

And how do you get a 50 foot pole to the page from hwy 10??  Will they deliver??

Pretty sure telephone poles are treated well enough to out last most of us. Not sure that he was suppose to do this but a guy down the lake we had built a retaining wall right in the water and they have been there for as long as I can remember. Not sure about the place on hwy 10? Just know we go by it every weekend it's on the northside of 10 some where pace Clear Lake.