Creek Culvert Project
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EddieWalker
Epic Contributor
As much as I like concrete sacks for this sort of thing, I think the voides under the pipes and the closeness to each other is the first priority. The good thing is that the worse case scenerio here is that the pipes will just wash downstream a bit if it gets that bad. More then likely, the water will just wash away the gravel between the pipes and he'll have to redo it. Even with proper spacing and compaction, Toolaholic is dead on with something to prevent the water from washing away the fill. Head walls or something solid to keep the water from wearing away the materal at the edges of the pipes.
Water is the never ending, never relenting enemy of all roads, buildings and everything else!!! Flowing water just makes it a thousand times worse.
Eddie
Water is the never ending, never relenting enemy of all roads, buildings and everything else!!! Flowing water just makes it a thousand times worse.
Eddie
schmism
Super Member
It should be noted that it doesnt matter what the FLOW is, it only matters what the VELOCITY is when it comes to the size of upstream riprap. The faster the water flows the more force it carries with it.
Addtionally the voids between the pipes at the bases as seen in
will likely be a countributing cause of a failer later down the road.
Addtionally the voids between the pipes at the bases as seen in
will likely be a countributing cause of a failer later down the road.
SnoFalls
Silver Member
like others have pointed out ... I expect this to fail.
Since this is a "seasonal" creek, have you considered a "concrete swale". Dunno if it worthy for ya, but many seasonal roads around me are doing this instead of culverts.
Basically make a dam, with a concrete overflow (sized correctly with proper head/tail walls), and you're set.
Since this is a "seasonal" creek, have you considered a "concrete swale". Dunno if it worthy for ya, but many seasonal roads around me are doing this instead of culverts.
Basically make a dam, with a concrete overflow (sized correctly with proper head/tail walls), and you're set.
OP
TNhobbyfarmer
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Well it looks like the consensus is that this is doomed to failure. That is the bad news. The good news is that I have lived without a raised crossing for many years and failure is not a devastating blow.
Plan B will consist of ripraping the fill on both the upstream and downstream walls; filling (as much as possible) the voids at the bottom of the pipes to lessen the flow of water between the pipes; and finally wait for a big rain. At that point, k sa-rah sa-rah, whatever will be will be. I'll report the final outcome.
Plan B will consist of ripraping the fill on both the upstream and downstream walls; filling (as much as possible) the voids at the bottom of the pipes to lessen the flow of water between the pipes; and finally wait for a big rain. At that point, k sa-rah sa-rah, whatever will be will be. I'll report the final outcome.
schmism
Super Member
if you could scrape off most of the cover, it should be fairly easy to back fill between the pipes with some fines by hand.
Ive gotten fairly good at backfilling the 3' deep 4" wide trench i made this weekend for water and power runs....
Ive gotten fairly good at backfilling the 3' deep 4" wide trench i made this weekend for water and power runs....
OP
TNhobbyfarmer
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Update: We got 1.8" of rain yesterday. I went to the creek to evaluate the culvert project expecting the worst. To my delight everything held up well and there was no visable washing or other damange. Based on the comments and concerns you guys had, I added riprap on the upstream and downstream vertical sides. Also, I blocked off the voids between the pipes as best I could. That should slow down the flow between the pipes. I forgot my camera, so no pics available on the riprap work.
When we get a real frog choker, I'll update again. I'm keeping my fingers crossed.
When we get a real frog choker, I'll update again. I'm keeping my fingers crossed.
EddieWalker
Epic Contributor
I don't expect any sort of catostraphic damage, but more along the lines of erosion that makes it impossible to cross the culverts. The water will have to flow for a period of time and work away at your fill around the pipes. It won't happen on a light rain, or slow moving creek, but when things get heavy and the creek starts moving millions of gallons of water, things will erode.
Worse case will be that the pipes float away down stream and create a log jam. Maybe they will just float off the the side and you can find them real easy.
Moving water never relents. It just keep working away at anything in it's path. You have created an obsticle with the culverts and fill material. Like most, you learn this the hard way. LOL I know, I've had some suprises that have cost me quite a bit of money.
Eddie
Worse case will be that the pipes float away down stream and create a log jam. Maybe they will just float off the the side and you can find them real easy.
Moving water never relents. It just keep working away at anything in it's path. You have created an obsticle with the culverts and fill material. Like most, you learn this the hard way. LOL I know, I've had some suprises that have cost me quite a bit of money.
Eddie
KeithInSpace
Veteran Member
Being as this is what I do for a living, this thread caught my eye.
All the previous posts seem to summarize the obvious. And you seem to be aware of the importance of proper backfill compaction. 24" HDPE Type S storm pipe (like you have) is VERY sensitive to backfill and relies on it almost exculsively for rigidity. In summer heat, I am 100% certain the pipes will deform under the weight of your bridge. And I would be a little uncomfortable driving a heavy tractor across them. If the pipe fails, it will fail catastrophically (collapse into itself)under the weight of one of your wheels and given the 2 foot diameter, that would put one of your wheels quickly in a 2 foot deep hole. Pretty scary to me.
I am also quite certain that, as Mr. Walker indicated, this entire project will end up 'down the creek' as the pipes WILL simply float away (eventually) during a large storm.
Unfortunately, I don't see any solution other than to reconstruct your bridge, leaving sufficient gaps between the pipes for them to be "independently" backfilled, rather than as a bridge unit with the gaps unfilled (as they so clearly are now).
Without any upstream watershed analysis, capacity is unknown. Assuming you are OK with this general configuration, I would suggest digging down on your natural crossing, "seating" the invert (bottom) of the pipe into the ground by at least 6 inches. This will slightly diminish the capacity of the system, but it will eventually fill with sediment, helping to weight the very light pipes down. This also diminishes the possibility of water getting under the pipe. Most of your capacity is in the "gut" of the pipe, so if you're good now, you'll be good even if they're buried 6".
If you can armor the face with rip-rap, that would be best. Concrete works good, too. But the biggest things are filling the gaps between the pipes (a solid 1.5 or 2 feet of solidly packed soil between each pipe would be very helpful) as well as "seating" the pipes.
All the previous posts seem to summarize the obvious. And you seem to be aware of the importance of proper backfill compaction. 24" HDPE Type S storm pipe (like you have) is VERY sensitive to backfill and relies on it almost exculsively for rigidity. In summer heat, I am 100% certain the pipes will deform under the weight of your bridge. And I would be a little uncomfortable driving a heavy tractor across them. If the pipe fails, it will fail catastrophically (collapse into itself)under the weight of one of your wheels and given the 2 foot diameter, that would put one of your wheels quickly in a 2 foot deep hole. Pretty scary to me.
I am also quite certain that, as Mr. Walker indicated, this entire project will end up 'down the creek' as the pipes WILL simply float away (eventually) during a large storm.
Unfortunately, I don't see any solution other than to reconstruct your bridge, leaving sufficient gaps between the pipes for them to be "independently" backfilled, rather than as a bridge unit with the gaps unfilled (as they so clearly are now).
Without any upstream watershed analysis, capacity is unknown. Assuming you are OK with this general configuration, I would suggest digging down on your natural crossing, "seating" the invert (bottom) of the pipe into the ground by at least 6 inches. This will slightly diminish the capacity of the system, but it will eventually fill with sediment, helping to weight the very light pipes down. This also diminishes the possibility of water getting under the pipe. Most of your capacity is in the "gut" of the pipe, so if you're good now, you'll be good even if they're buried 6".
If you can armor the face with rip-rap, that would be best. Concrete works good, too. But the biggest things are filling the gaps between the pipes (a solid 1.5 or 2 feet of solidly packed soil between each pipe would be very helpful) as well as "seating" the pipes.
BTDT
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Looks like the simplest quick upgrade would be to pull out the middle culvert. This would allow the dirt to fill in around culverts on either side, then set middle culvert back in depression (it would stick up higher than the other two), then put fill over top of all 3 again. Good luck.