Landscaping after Mudslide... please help

Gus_Zone4(4)January 31, 2014

We moved to this house in 2009. In 2011 we had mudslide on the hill behind our house. On a March morning we woke to find the hill had slipped several feet toward the deck and over a few weeks time the hill moved about eight feet closer and was touching the deck.

We hired an excavator friend to remove the mud/green clay from the seepage/spring. We installed a French drain to carry away new water from the seepage after future rains (which has been working well).

I placed two empty oil drums into the left side of the field, filled with black dirt and punctured their bottoms to allow drainage. Then we put down fabric and covered it with 1.5" - 4" rock 3 - 5' deep. Afterwards we also put a couple pieces of limestone rock on the field.

Truth be told, life got busy and we have not done anything since covering it with rock, but now beautifying this area will be a priority this summer. I would love to erect a stone wall but feel the foundation soil is too unstable for that to be a long term solution. Tool-wise we have a track loader at our disposal. Would prefer to do the labor ourselves.

I will post a series of pictures. The slip is half moon shaped, approx 40' wide and maybe 30' uphill to the farthest reach.

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Gus_Zone4(4)

A better sense of scale with this picture.

    Bookmark   January 31, 2014 at 2:17PM
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Gus_Zone4(4)

This is the only picture I could find of the rock pile that needs help. Sorry it isn't very good. I was really focusing on the nice half-harvest of the shell beans in the trailer. The rest of the pile is buried under > a foot of snow at the moment.

After all the trouble of getting a good porous rock over the fabric above the clay, I have been really resistant to my wife's idea of putting down black dirt and trying to grow stuff there. I feel I may have to yield on that. Initially we thought we'd try to arrange some rocks for seating / planters and make fire ring but???

I should mention that blips of green clay at the foot of the pile have oozed out that I should scrape away. One blip is ~18" dia and maybe eight feet long and another that is smaller.

Any suggestions will be appreciated. Thanks for looking.

Gus

    Bookmark   January 31, 2014 at 2:32PM
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yardvaark

There is much that cannot be understood though the pictures and your description. Obviously, you have done a lot already, but are faced with issues. Doing things incorrectly could mean more issues and costs down the road. I think you should consult a soils engineer locally and get some good advice. Acting on incomplete advice may cost you much more than what you think you are saving. Fortunately, you have access to that mig muscle machine. In order to be effective the muscle must be controlled by a brain (engineer) that knows what it's doing.

    Bookmark   January 31, 2014 at 5:24PM
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yin49

Some rock,shrub would help.

    Bookmark   January 31, 2014 at 5:58PM
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Gus_Zone4(4)

A clarification is in order. The height difference is probably 15'; the 30' is the front to back dimension. The soil is a clay called "Dakota shale". It is inherently unstable. The house was built in the 1880's and remodeled several times. The seepage from the hill behind is never going to be eliminated. My daughter is a soils engineer. We have had two rains-of-the-century in the past 5 years. It held up well to the second one, since our handiwork.

I am not seeking an erudite lecture on the multitudinous risks from the Yardvaark, but rather aesthetic suggestions from friendlies.

This is my first posting (I believe) on Gardenweb. I have enjoyed reading many things here. Various opinions abound. I am primarily focused on vegetable gardening in SE Minnesota, but this is a(n aesthetic) topic of great interest to both my wife and I.

A Buddha figurine arrived for Xmas, which we are expecting to put outside in the "garden" when we have it more finished.

Zone 4 temperatures in winter (-20 F) limit our choices in planting. This spot will receive 6-8 hrs of sunlight in the summer. There is no topsoil yet. Wild raspberries and whatnot have healed the scars at the edge and are draping inwards.

We have basically an unlimited amount of trees (dead or Boxelder volunteers to be thinned out) which perhaps we could use as a sort of Hugelkulture (sp?) base over fabric.

Vin49-- Yes! I was thinking of some kind of Junipers in the two barrels? I can get more Limestone, too.

    Bookmark   February 2, 2014 at 5:24PM
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yin49

Yes. May you like a hierarchy garden.

    Bookmark   February 2, 2014 at 9:30PM
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sc77

You need a retainer wall to keep that under control. Since you mentioned that the ground is too unstable for a stone retainer wall, I'm thinking that a wooden retainer wall would work well.

This particular design would be good, because you could anchor the vertical wooden posts deep into the ground and pour concrete base. Even if there was some settling, shifting of the soil it wouldn't compromise the integrity of the wall as it might with stone.

If not retainer wall, then I would just cover the whole slope with juniper groundcover. Evergreen and does an excellent job of preventing soil erosion/slipage

Here is a link that might be useful: Wooden Retainer Wall

    Bookmark   February 2, 2014 at 11:03PM
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marcinde(7)

"I am not seeking an erudite lecture on the multitudinous risks from the Yardvaark, but rather aesthetic suggestions from friendlies. "

No one with any sort of professional background is going to tell you what color to paint the walls if the roof appears to be falling off. Your response is incredibly rude and you owe Yardvaark an apology.

    Bookmark   February 5, 2014 at 7:33PM
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yardvaark

If one concludes describing several paragraphs worth of engineering challenges with "Any suggestions will be appreciated." ... I guess they mean aesthetic suggestions ONLY! But "erudite" ... "lecture" ... "multitudinous risks" ... unfriendly ...?

    Bookmark   February 6, 2014 at 3:29AM
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pls8xx

I for one appreciate the in-your-face honesty of the OP. It means I, Yardvaark, and probably every other professional is saved from wasting any time assessing the problems his slope presents.

    Bookmark   February 6, 2014 at 6:23PM
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Suzi AKA DesertDance Zone 9b

I like the retainer wall plan the best. We are on a big slope and there are a lot of retaining walls. Some are made of railroad ties and others with block wall. They hold the slope back, and junipers (which drive me nuts) help hold the dirt from sliding. I love the rosemary cascading over the walls, however. It is always in bloom, and it's roots hold the dirt!

Good luck with your quest!

Suzi

    Bookmark   February 6, 2014 at 8:10PM
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deviant-deziner(Oh zone)

old wooden pallets tied together with shoe strings , make that light brown shoe strings to match the mud. - that will shore up/ retain the hillside nicely , from there pretty pink flowering plants would work well.

    Bookmark   February 8, 2014 at 2:55AM
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rosiew(8 GA)

to OP - sorry you're having to deal with this huge problem. Further reading on hugelkultur (no E on the end) could perhaps benefit you greatly.

Google hugelkultur - lots to read there, many from GardenWeb. It will be labor intensive, but maybe you can use big equipment to help.

Looking forward to following this.

    Bookmark   February 8, 2014 at 10:28AM
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nandina(8b)

When I first viewed the pictures you posted lots of thoughts came to mind. The first was that I could not answer your question because there are many unknowns to which there may never be answers, just the experience of moving through the years ahead, attempting corrections and watching the results.

So, the following thoughts will probably not help. But, they are the best I can do.

Such as, why did this slope let loose suddenly when there certainly must have been a number of 100 year storms since 1880? Has something happened at the top, some type of construction, perhaps.

The following may not be correct but it appears that the tree growth on the hill is fairly young. Perhaps your daughter can figure out if former owners have cut back trees, leaving trunks and roots, to reduce weight on the hill.

Over the years I have developed great respect for heavy machine operators who work on all types of soils and problems in a general area, often under the direction of civil engineers. They are skilled and have a vast knowledge of land. Does your excavator friend have any suggestions for a fix?

The only time I have been involved in a very similar situation the 'fix' was a 3' deep poured cement wall foundation the width of four cement blocks with rebar inserts, plus careful drainage. Wall height was about 5'. 45 years ago. Still standing strong.

    Bookmark   February 8, 2014 at 11:01AM
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