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  1. #1
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    Dirt Road to Trail: Drainage Problems

    Here in Southern California is a gem of a trail called Monroe Truck Trail. As the name implies it is an old dirt road that has been "let go" and it has evolved into this really great single track. Most of the trail stays in pretty good shape. However there are a few spots that are becoming issues.
    Because its an old roadbed, it is all insloped. The road engineers did however do some grade reversals with outsloping. At each of these outslopes metal drainage troughs were installed to get the water away from the road. In most of the spots it has worked out well, even without any maintainence for many years. I was able to go and remove sediment and vegetation to the mouth of these drainage troughs, and they are functioning as designed and effectively.

    There are, however, a few spots that need some special attention.

    Here are some pics.





    At this particular drainage area, the trough was been under eroded. The edge of what is left of the road is about six feet away from the opening to the trough.

    Any ideas about how to deal with this?

    I can't get any power equipment into this location, so everything will need to be done by hand.

    Thanks for any suggestions.
    Cycle tracks will abound in Utopia. ~H.G. Wells

  2. #2
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    I'm not sure what I'm look at, can you post some wider photos?

    Think about where the water is coming from, and where it wants to go and design around that logic.

  3. #3
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    i'm having a hard time understanding how those metal troughs are supposed to be working in this pic. It looks to me like that metal is collecting organics and flood water by creating a dam?
    At any rate, my recommendation would be if you can harvest enough rock to fill in the eroded area and replace the road grade to a reasonable point. If there is a higher area to the side of this trail you could also build a new re-route around, and just close off this eroded trail section.

    *edit* Is that a culvert? Where that metal piping is providing flood drainage underneath the road bed, from one side to the other?
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  4. #4
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    Sorry about the confusion.
    This first picture shows the situation best. The photo is taken from the downhill side of the trail. I am standing on the top of the grade reversal. The water would be heading down toward the camera. The roadbed is insloped down to the right, untill the bottom of the reversal where the water then flows off to the right. The drainage trough used to be at the outsloped side of this dip. In the years between maintanence the water eroded below this trough and now the water flows off the trail, into where you see all the organics, and finally under the trough, making its way down the mountain. Unfortunately the water is now eroding the road be away from the trough and into the trail.

    thanks again.
    Cycle tracks will abound in Utopia. ~H.G. Wells

  5. #5
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    We have dozens of these flumes in very similar conditions throughout the property I currently manage.

    Most of this is caused by people not servicing the flumes (keeping them clear of mud and debris, thereby creating a dam that blocks and undermines the top of the flume.

    Many of them get buried by annual grading by the utility companies and go unnoticed until a failure like you show in the picture.

    In most cases we have been able to shore up the damage with rip-rap (4" to 8" rocks), then recompact soil to re-shape the entrance. The rip-rap acts very well for two purposes.......to stabilize the entrance beneath the compacted soil, and to act as a means to slow-down and disperse the water in the event that the soil gets washed away in a severe storm.

    In severe cases, it may be necessary to dig up the entire flume and move it inward towards the trail, then re-route the trail slightly away from the potential slide area, and re-work the grade reversal. Also add a few water-bars to slow the water down prior to it hitting the flume.

    Either way......just the presence of the flume at least gives you something to work with, and once properly repaired and maintained.....the structures can perform very well for years.


    Addition: The ones in your photos appear that they would perform well with the addition of rip-rap to fill the hole, then re-shape the entry to the flume with compacted soil.


    One more addition: A very important part of these flumes that many people overlook when they install them is to add a dispersal field at the outflow end of the flume (rocks, boulders, etc....). This prevents the water from underming the end of the flume which in many cases causes the entire structure to slip downslope, thereby creating a gap at the top edge for water to further undermine the flume from the top.

    If the entire flume is already undermined, then the best solution would be to pull it out and re-position it like a new installation.

    There is a really great monthly publication called erosion control that has a ton of information of these types of structures.

    I can shoot you some of the documents I have on hand regarding these structures if you wish.

    Just shoot me a e-mail to amaywhort@irconservancy.org

    Hope this helps.
    Last edited by JamR; 12-03-2008 at 08:12 PM.

  6. #6
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    I'm thinking filling the eroded soil is going to be the best option. It's gonna be a ton of work. I bet it will take more than two cubic yards of fill. That's a lot to collect and transport when working solo.
    I think I'll make a call to the forest service and see if there is anyway to get some help.

    Thanks.

    Any other solutions I haven't thought of?
    Cycle tracks will abound in Utopia. ~H.G. Wells

  7. #7
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    A couple of fixes with minimal tools.

    It's kind of hard to tell from the photo but it looks like you might be able to move the whole thing uphill a few feet. Dig a new bottom for the grade reversal and use the fill to widen the trail at the erosion point. That would depend on you being able to move those troughs.

    Another solution might be to let the water drain off the left side of the trail into a catch basin and put a culvert under the road that sticks way out into the trough. you'd really have to keep an eye on the catch basin for debris and clean it regularly.

  8. #8
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    Quote Originally Posted by Trail Ninja
    A couple of fixes with minimal tools.

    It's kind of hard to tell from the photo but it looks like you might be able to move the whole thing uphill a few feet. Dig a new bottom for the grade reversal and use the fill to widen the trail at the erosion point. That would depend on you being able to move those troughs
    Unfortunately the troughs or flumes are anchored into the side of the mountain pretty well. It would take a lot of work to move them. I think If I could move them it would be to move them up the hill a bit then backfill.

    I was able to get in contact with the local wilderness manager/trail superviser for the local national forest. We're going to take a walk this next week and he says he's got access to volunteers that may be able to help. Hopefully we can come up with a good game plan. With luck I'm hoping to get this rolling before the real rainy season here which is in January and February. Then again those months are approaching rather quickly.
    Cycle tracks will abound in Utopia. ~H.G. Wells

  9. #9
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    ...just a thought... locate a tree nearby and, assuming its removal wouldn't jeopardize the surrounding area, replant said tree in the eroded section with a ton of "back-fill" including native-plants and vegetation to absorb H2O and hopefully, elude erosion.

  10. #10
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    Luckily I was able to meet with the local trail advocacy volunteer group this last Saturday. I walked the trail and talked about many different locations on the trail. With this particular site, they recommended gabions. I think it will be a great solution, labor is the only problem. But it seems that they have sources for that.
    I am also a Environmental Science teacher. I smell extra credit. I'm still holding out hope that we can get this going before the big rains.
    Again. Thanks for the input.
    Cycle tracks will abound in Utopia. ~H.G. Wells

  11. #11
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    Quote Originally Posted by chumbacabra
    , they recommended gabions.
    That's a good application. We put in a ton of em at Colonnade. My only suggestion is you take a little time and place the rocks instead of just tossing them in. So toss in a bunch then start placing them . Since you will have to apply support ties inside the gabion it's likely you'll be placing more than you throw anyways. That way you won't get any shifting/settling of rocks. That will prevent any weird stress anywhere along the cage and it should last forever.

    We did a better job on our gabions than the City Parks contracter did on their section of the park. Our reason was for aesthetics so we took more time to lay flatter rocks on the face side of the gabion. But for your application that won't be necessary unless you're trying to impress the wildlife on the slope...

    http://evergreenmtb.org/wiki/uploads...052b-small.jpg

    We even created a double diamond feature called G-Line for gabion, on top of a row of gabions. It's holding up well.

    http://evergreenmtb.org/wiki/uploads...e-mike-jon.jpg
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  12. #12
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    Great job. Those look really great and I'm sure they'll outlast us. I gotta get up there and ride that stuff. What a fun way to improve skills.
    Cycle tracks will abound in Utopia. ~H.G. Wells

  13. #13
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    If your planning on doing a trail day and it's approved by the Forest Service. I think incycle bike shop would be a great place to recruit volunteers. I use to work at the shop and the owner Mark and I would talk about doing needed work on the local riding spots, but we never came around to talking to the right people. He would love to advertise for you im sure. I loved riding MTT.

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