Pasture drain

[JeffInCO]

I've been working on a project for a while to drain a low spot in my pasture. I dug a trench almost 400 feet long with my backhoe, ranging from 2 to 4 feet deep, so that the bottom has a good slope. In some places along the way, there is groundwater at the bottom of the trench. The entire bottom of the trench is clay, and when it is wet, it has no structural capabilities whatsoever... when I first dug the trench, I could sink halfway to my knees when walking in it.

I plan to place a pipe at the bottom of the trench.

I started adding rock -- nominally about 3/4". This seems to help in some spots, but probably about 20 tons of rock later there are still still spots that are structurally pretty week. I tried using a "Jumping Jack" to push more rock into those spots, but this really just caused "liquifaction" -- the entire ground undulating without really getting any harder with the rock.

I want to make sure that there is adequate support at the bottom when I backfill, so that the pipe doesn't become deflected.

Any ideas to stabilize the bottom? I found a few research papers which indicated adding cement to wet clay might give it some structure. Anyone tried this?

Thanks,

Jeff

 

[leonz]

Hello Jeff,

adding cement as a stabilser is common in areas
with poor ground where it is pumped in and mixed with
a large diameter soil auger mounted on a crawler crane.

You could add cement but it would get very expensive
with regard to soil stabilizing the base of the trench for
your drainage needs as youu would need a small rototiller
to mix it as you poured the sand mix or straight portland
cement out of the bag.

In order to do this properlly you need to purchase the
perforated drainage pipe with the soil stopping fabric to
keep the drains open for you, or purchase the landscape
fabric from Agricultural Supplies, Fabric Structures, Equine Buildings, Grain Storage, Livestock Buildings from FarmTek
to wrap around the drainage pipe and prevent it from
plugging on you. We used their best fabric and it is
very easy to use and it is very easy to handle.


The key for trench drainage is to set the pipe at the side
of the trench to lay it in place by shoveling dirt on it to
hold it there while back filling to keep it in place as it is
very light and squiggly.

I am unsure if any of the white PVC septic drainage
pipe available has holes around the entire diameter or not
but if you spral wrap that pipe with fabric and use duck tape
to hold it while you set the pipe you can simply join
the pipe ends with the PVC glue wrap it and just set it in the
trench with no specila care and then bury it.


The key having the rise and run to allow good drainage
for your trench.

:thumbsup:

 

[Rustyiron]

How about aproaching this the other way, in your really soft areas, jump up to heavier pipe (sch 40 or even corr. galv. metal) and drill the holes if you can't find perf. Sounds like you spent some $$ and time on stabizing the clay, surrender and beat it the other way!

 

[JeffInCO]

Thanks for the ideas...

I guess it would take a lot of cement to stabilize adequately, and I probably couldn't mix the cement in by hand with a shovel as I probably need to go down to some significant depth. The trench is too narrow (about 20") for even a small rototiller.

As for using stiffer pipe, I don't think schedule 40 would be adequate. Possibly, corrugated metal would work so long as it has solid support in a few spots along the length of each piece. However, I wonder if corrugated steel would quickly corrode in a constantly wet environment like this.

Jeff

 

[leonz]

The corrugated pipe would last a few years but the
combination of water and oxidation would rust it out
and then it would collapse on you unfortunatly.

You could mix the soil with a narrow mantis rototiller but
the tiller would be very aggressive where it pulls all
the soil to the rear of the tiller at all times and would
not mix the Portland Cement very well.

I think you will be better off if you purchase the tubing
with the filter sock wrapping for your ditch to solve your
pasture drainage as you can set it in and anchor it along
the edge of the trench then back fill and be done quickly.

 

[JeffInCO]

Leonz,

I'm not sure that I see how placing the pipe on the side of the trench really solves the problem... The pipe still needs to be supported from underneath, and the bottom of the side is just as squishy as the bottom of the middle. It does make sense that the pipe will try to move on me, so anchoring it somehow before backfilling definitely sounds like a good idea.

I do intend to use perforated plastic pipe -- probably the smooth-walled type, wrapped in geo-textile fabric as you described.

Thanks,

Jeff

 

[leonz]

Hello Jeff,

When you anchor the pipe in the trench by shoveling dirt on it to hold it in place you keep it from being shoved by the back fill as it is dumped in the trench, that is the secret.:thumbsup:



_________________________________________________________________
Once you go flail you never go back:licking::drool:

 

[Haoleguy]

Jeff - Does this trench ever dry out in the summer or do you just have a permanent high water table? I recently did 3 trenches each at 250ft in length and in some cases had to deal with areas of soft ground but not as bad as yours sounds.

My first choice would be for the trench to dry out and then move ahead with your drainage pipe as planned.

Second choice would to be lay the fabric covered pipe in the trench, if the slope integrity still exists, and then add soil to the dry areas first to put significant weight on the pipe. This should keep the pipe taught before slowly adding soil to the soft areas. The water will then drain from the area and in subsequent years the pipe will intercept the water before it has a chance to soften the area. An alternative would be to pound in a few stakes and zip tie the pipe to the stake to achieve the same taught pipe across the soft areas.

Third choice, and related to second choice, would be to use a heavy geotextile fabric in narrow format at the bottom of the trench. Staple in firm areas. Then place fabric covered pipe on top and fill soil on firm areas only first. Then proceed with the softer areas. The idea again is to have the fabric bridge the soft area and form a straight downhill run that will firm up with time as water is moved away.

Good luck, Gary

 

[Army grunt]

Fill that ditch with large stone. (like from a stone wall. )Dig a second trench after a mounth or so. before fall rain I rember before the silt cloth we used straw in the bottom then stone an pipe.Just my $00.02.
Army Grunt

 

[JeffInCO]

The trench mostly never dries out completely. I have a high water table in this spot. I think I'm going to dump more rock in this weekend - one last attempt to stabilize it.

Also, I have limited ability to slope it. I can get about 1/2 a percent of grade, which should be enough with 6" pipe (should flow at 2.5 ft/sec, enough to scrub the pipe walls)

Jeff