The trench vs the rain

[Old Guy in Tenn]

4 weeks ago in Tennessee we used a ditch-witch to dig a 2-foot deep by 4 inches wide trench about 450 feet long, from the house down to the spring. 150 feet is on our rolling hilltop, the remaining 300 feet are down a steep hillside though the forest. We placed the pipes and wires in the trench and started filling it back up.

On the first try we started from the bottom, packing it down with a hand thumper as we went. We were 3/4 of the way up the hill when the thunderstorm hit. In 20 minutes the trench was totally open again from the runoff, and the dirt was scattered evenly over half an acre of forest floor. The downpour's runoff got into the trench, slowly scoured it deeper, and then became a rushing torrent of destruction.

The next day we hired a college kid to help and started over, this time filling the trench from the top down, again packing it down hard as we progressed. We were well over half way down the hill when the rain hit us again. We stayed out in the rain and tried to divert the water where we saw it starting to erode. We failed. Maybe if we had 50 helpers we could have held our own.

My son has been trying to fill the trench for the last few weeks. He has built water bars and ditches to keep water out of the trench, but the water overwhelmed and destroyed them. He buried boards on edge trying to divert it, but the water dug under and flowed over the boards. He laid strips of plastic dropcloths over the trench, but the water found a way under and washed the dirt away.

The trench goes mostly straight down the hill, although for much of it there is a slope that brings water in from the side. This water from the side was one of my son's biggest problems. He is leaving tomorrow morning for Texas, and I will arrive in a week to pick up where he left off. It will almost certainly rain again while no one is there. I am at a loss for what to try next. I think I can salvage the hilltop, but am not even certain about that.

Anyone have any suggestions?

 

[KiotiKowboy]

Perhaps creating a series of gravel dams inside the trench would stop the runaway erosion?

Sounds like what you need most is a few DRY weeks.

 

[CalG]

Don't you have a tractor for back filling?

 

[Industrial Toys]

Man do I know about stuff like that. I have buried a lot of services on this property and quickly learned that you close it up fast. One time, I partially backfilled thinking that was good enough. Then the rains came and the pipes floated right out of the fill to the top!

 

[Old Guy in Tenn]

The Cub is currently out of commission, but does not have a loader in any case. The big problem is the steep stretch through the woods. Much too steep for any tractor. We used a come-along and lowered me and the ditch-witch one click at a time while cutting the ditch.

Yes, what I really need is a couple of dry weeks to let everything firm up. In the meantime, though, I need to keep it from washing away.

 

[KiotiKowboy]

Just throwing ideas at the wall ...

I've not worked on anything that steep but ...
Seems like filling it half way with gravel would allow water flow below the top fill until it all settled. Then you could put another layer of dirt on top later in better weather.

 

[LouNY]

If you can get it filled and throw a hay bale across it a lot of time the hay bale will soak up the water and silt to make a small dam. It may take a bale every 20feet where it's steep.

 

[3Ts]

Man do I know about stuff like that. I have buried a lot of services on this property and quickly learned that you close it up fast. One time, I partially backfilled thinking that was good enough. Then the rains came and the pipes floated right out of the fill to the top!

and broke some of the fittings. This was a sewer pipe that "T'ed into my septic tank, but fortunately the contractor used a fernco fitting so the pipe rotated up and didn't flood the tank.

No real suggestion for you other than what you already know. Fill the trench and pack it down as quickly as possible, and try to keep the water off the surface of the trench.

 

[RNeumann]

Homepage | Weather Underground

And a Wacker packer (slang) or Wacker Rammer (real name).

 

[Tough Luck]

Welcome to East Tennessee...worst weather I have ever seen in the ten years I have lived here. No one can predict the weather here. The local so called meteorologists only repeat what their 'weather model' tells them. I've had 3"/hr rain events with a forecast of 'slight chance' of rain. Couple that with the red clay they call soil here, and you have a runoff disaster. You may try to install some water bars. Good luck with your trench.

 

[coldsteelva]

I don't know how much work (or cost) this would be, but would it be possible to grout/gunnite/shotcrete the trench (or a portion)? If the hillside is as steep as you say, now that you disturbed the soil it will ALWAYS be the path of least resistance for the rain and will erode forever.

If that won't work, could you perhaps fill the trench with gravel and dry cement to lock it up? The water would be able to flow/drain possibly without eroding.

 

[Deere Dude]

I don't know how much work (or cost) this would be, but would it be possible to grout/gunnite/shotcrete the trench (or a portion)? If the hillside is as steep as you say, now that you disturbed the soil it will ALWAYS be the path of least resistance for the rain and will erode forever.

If that won't work, could you perhaps fill the trench with gravel and dry cement to lock it up? The water would be able to flow/drain possibly without eroding.

That would be my advice also. But if the ditch is running on the bottom of a contour, maybe nothing will work. I really doubt there would be a problem if run on a ridge so much less water could inundate the ditch. Right now your ditch is probably getting deeper from erosion.

 

[Old Guy in Tenn]

Good ideas. Thank you all. I am lucky at least that the pipe is full of water and so has not floated up. The wacker looks good, but $2000 is a bit much for my budget. NE Tenn weather! Record rain, and it seems most of it fell on my place. I think that I will fill, hand thump and mound the trench, and add some serious water bars and ditches to keep some of the water away. Maybe add some sod at the top where it is relatively flat. I have a week to think on it. Keep the ideas coming.

 

[aczlan]

Good ideas. Thank you all. I am lucky at least that the pipe is full of water and so has not floated up. The wacker looks good, but $2000 is a bit much for my budget. NE Tenn weather! Record rain, and it seems most of it fell on my place. I think that I will fill, hand thump and mound the trench, and add some serious water bars and ditches to keep some of the water away. Maybe add some sod at the top where it is relatively flat. I have a week to think on it. Keep the ideas coming.

Call your local equipment rental places. They will probbaly have one that they rent out.

Aaron Z

 

[s219]

I have had heartbreak from rain washouts on a couple projects, but this sounds like a doozy. I wonder if you could get some sacks of bentonite for the trouble spots, and if it would be any better than the native clay. Another option, if you can get it partially filled, might be to drop a slotted drain tile pipe in there with gravel and septic paper, that way if water wants to get in there you won't fight it. Sounds like you have created the ultimate drain path for the terrain and nature is hard to fight against.

Is this for a water source from the spring? If so, I might double down on the bentonite idea, especially towards the bottom. Don't want flowing surface water to be focused on that spring and possibly contaminate the water source (same reason well pipes are grouted).

 

[EddieWalker]

No amount of compaction is going to solve this issue. The fill material will remain softer and looser then the undisturbed soil for all eternity. What you need to do is create a series of dams to stop the water from building up speed and eroding your fill dirt. This is the same thing that is done to fill in erosion ditches on land and drainage ditches along the roads. Eventually when grass grows over the area, that will stop all of the erosion from happening.

You have two choices in matrials. Rip Rap is basically broken up rocks, concrete, bricks, or cinder blocks, or anything that will not wash away. I even use broken tile. Use this to fill in the ditch in different places along the way. Considering how bad it is, you might need to do this every 20 feet, but that's really something that you will have to figure out on site. I've found that all I need to do is slow the water down in a bad spot and that will solve all my issues.

The other choice that woks well is a 40 or 50 pound sack of concrete. You just put the entire sack with the paper still on it into the ditch. The goal is the same, you want to stop the water from building up speed and washing out the soil.

Do not waste your time trying to get dirt to remain in the hole without something to stop it from washing out.

 

[Richard]

^^^ I agree with what Eddie said.

About 10 years ago, our neighbors bought 40 acres (which is when they became our neighbors). They were going to develop said land and started to put a couple culverts and a road in.

If it wasn't so sad & messy, it would have been funny..... but they had the requisite road building machinery there.... getting to work on it and it would torrentially downpour. The running water would cut trenches in the road base and wash out into the existing country road and would in part, wash into the lake (TVA's lake and they don't like that kind of stuff!!)

I don't recall exactly, but I want to say it literally took them something like 6-10 months to get the road finally paved as each & every time they'd get it graded just right in preparation for paving, we'd get a monsoon.

That road was a terrible mess and cost them a fortune, then of course, they get to give it to the county. Of course, right after the road got paved, we had pretty weather for 2-3 months with normal rains instead of the monsoons. It really seemed as though God was trying to tell them something.

 

[Old Guy in Tenn]

Great information. Thank you. I expect to arrive there Saturday evening, and get to look at the problem firsthand. With your help I should be able to make an impossible situation merely difficult. Thanks again.

Motrin. I gotta' remember the Motrin.