Retaining wall ideas Needed - steep slope with only top access

[tractchores]

I've got a project coming up and am trying to figure out how to get it accompished. I have a flat area that drops off steeply (45 degree plus slope) for probably 10 vertical feet then levels out a bit (25 degree slope) and ends in a lake. My challenge is I'd like to secure the top so it is flat and a fence can be installed. The kicker is that I cannot really access the bottom of the hill and am space constrained due to wetlands restrictions. The likely move is to cut into the hillside, go across it then build up the wall and anchor it in. The issue is that to do this I'll probably end up in the wetlands and will have a major project. Subcontractor estimates have been around $20k (the wall is 75' long). Top of the hill is a pool and pool deck, so cutting back from the top then rebuilding isn't really feasible with the size machine I can get in there.

My questions:
- Anyone have creative ideas on how to put some kind of retaining wall without doing a big cut into the hillside?
- Anyone ever anchor a retaining wall using pillars? I was thinking I could dig down or use an auger and put sonotubes and concrete down and then anchor the wall to that.
- Anyone ever do one of those walls that involves just placing large flat rocks on the slope and embedding them (looks like tiles). I can't find any info on that technique.

Equipment i have easily available:
Kubota B2920 with backhoe and FEL
I can rent all kinds of attachments locally including an auger
Can rent an excavator, but am very size constrained due to the pool

Any ideas are welcome! Thanks

 

[blackdog2086]

What about a steel seawall? The panels are interlocking and are pounded in by a post type pounder. I'm far from an expert, I've just seen them. My brother has one about 120' long at his lake property. It was there when he bought the place so I have no idea about price.

 

[dragoneggs]

What about a steel seawall? The panels are interlocking and are pounded in by a post type pounder. I'm far from an expert, I've just seen them. My brother has one about 120' long at his lake property. It was there when he bought the place so I have no idea about price.

I like that idea... I have a similar problem with access on my steep slope. Interested to see some solutions here.

 

[woodlandfarms]

I get the feeling this won't work but my neighbor added a good 5000 sq ft to his very hilly property. Took a big track hoe but he put these down like legos. The blocks themselves are very cheap, made by your local concretes supplier usually out of leftovers in concrete trucks. Cost is the delivery and the track hoe.

Pre-Cast Concrete Products (Second Row, large concrete blocks)

 

[Egon]

What kind of material and wetness is the hill.

 

[MikeInEburg]

Look at Gabions - essentially wire cages filled with rock. They come in many sizes, such as 4'×4'×8', and are designed to be stacked. Macaferri is one manufacturer that happens to be located near me.

 

[check]

I gave a similar problem, with a creek (that I can drive into with my Kuboat BX25) at the bottom of the slope. Was thinking of pouring a sloping cocncrete wall, and maybe embedding some decorative stone in the concrete while it is stiffening up. But will the wall stay where it is, or will the (sandy) soil underneath eventually push the wall upright over time, whereupon it will topple over into the creek?

 

[Danny C]

I have built countless retaining walls as a contractor. Everything from treated wood to gabiens to Redi-Rock to poured concrete to stone to boulders.

Your budget, desired longevity and desired look will determine what type of wall to install. I highly recommend Redi-Rock which is similar to the product recommended in a post above. They work due to their mass and thus use gravity. They should never be made from left over concrete especially when they will be exposed to freeze/thaw cycles and should be air entrained.

I have used Hubble earth anchors (used on power poles) to straighten and anchor old walls.

More detailed info and we can likely help point you in the right direction.

Danny

 

[newbury]

And we also need pictures!

 

[Beltzington]

Look at Gabions - essentially wire cages filled with rock. They come in many sizes, such as 4'×4'×8', and are designed to be stacked. Macaferri is one manufacturer that happens to be located near me.

+1 they could be filled and lowered from the top one at a time.

 

[s219]

Yeah, pictures would be great. What is the main goal? Is it to stabilize the bank?

Around here, we would place rip-rap rock (football to basketball sized). It's normally done by machine loads dumped from top, but may need hand/manual work in some cases or to fine-tune the spread. This is done to stabilize slopes and banks, prevent erosion, establish shorelines, etc. Good stuff. Can be expensive, but often is the best approach. Sometimes geo-textile cloth is placed under the rip-rap.

I am fortunate that the creekside bank on our property is stable. It's about 40' high and 45-50 degrees slope. All covered with vegetation, 50+ year old trees, and decent leaf-litter mulch/loam surface. Underneath is sand, so it is potentially fragile if disturbed. Just a 1/2 mile downriver from me, the banks are still evolving. My friend had to spend $50K to cut his bank back to a stable angle and add rip-rap and hardwood mulch, along with shrub plantings.

 

[Streetcar]

I gave a similar problem, with a creek (that I can drive into with my Kuboat BX25) at the bottom of the slope. Was thinking of pouring a sloping cocncrete wall, and maybe embedding some decorative stone in the concrete while it is stiffening up. But will the wall stay where it is, or will the (sandy) soil underneath eventually push the wall upright over time, whereupon it will topple over into the creek?

What is the slope of the soil,
Is the creek stabile or moving? Scour at toe of the wall can cause problems
You will need some method to drain water behind wall

 

[tractchores]

Thanks for all the great replies. I tried to answer all the questions below apologies in advance for a looong post.

What about a steel seawall? The panels are interlocking and are pounded in by a post type pounder. I'm far from an expert, I've just seen them. My brother has one about 120' long at his lake property. It was there when he bought the place so I have no idea about price.

I'll have to check into these, this could be interesting. Not sure if I could get the equipment to pound it in to the area given space and weight constraints due to the pool deck.

What kind of material and wetness is the hill.

Good question. The soil here is primarily clay with an unbelievable number of rocks. The rocks could be a real issue with this one, its possible I'll hit something immovable, but I believe the current slope is mostly fill from the house site, so hopefully no car sized boulders. In terms of wetness this is a well drained hill, so soil conditions are dry. Uphill from the site is the pool deck and pool, then above that 2 different retaining walls with good drainage and the house, which is longer than the retaining wall area. The house has extensive french drains. The net is that there should be very little if any water flowing through the area. I would want to have some drainage with the wall.

Look at Gabions - essentially wire cages filled with rock. They come in many sizes, such as 4'×4'×8', and are designed to be stacked. Macaferri is one manufacturer that happens to be located near me.

Thanks - did not know the name of these, but have heard of them. I wonder if they require a base for the toe pressure though? This is interesting because I have a really large number of rocks and it'd be good to put them to use...

I have built countless retaining walls as a contractor. Everything from treated wood to gabiens to Redi-Rock to poured concrete to stone to boulders.
Your budget, desired longevity and desired look will determine what type of wall to install. I highly recommend Redi-Rock which is similar to the product recommended in a post above. They work due to their mass and thus use gravity. They should never be made from left over concrete especially when they will be exposed to freeze/thaw cycles and should be air entrained.
I have used Hubble earth anchors (used on power poles) to straighten and anchor old walls.
More detailed info and we can likely help point you in the right direction.
Danny

I did take a look at redi rock when I was talking to contractors about the job along with a few other types of pre-formed blocks. They all seem promising. This area faces the lake and I'm about the only person ever on the lake, so the aesthetics from below are not a concern. With all the retaining walls of this type the big issue was having enough of a flat area at the foot of the wall to handle the toe pressure. That means making a sizable cut into the hillside, which given the proximity of the wetland boundary creates issues. I was thinking maybe some pillars could handle the toe pressure and eliminate the need for a cut. Ever see anyone do anything like that?

Yeah, pictures would be great. What is the main goal? Is it to stabilize the bank?
Around here, we would place rip-rap rock (football to basketball sized). It's normally done by machine loads dumped from top, but may need hand/manual work in some cases or to fine-tune the spread. This is done to stabilize slopes and banks, prevent erosion, establish shorelines, etc. Good stuff. Can be expensive, but often is the best approach. Sometimes geo-textile cloth is placed under the rip-rap.
I am fortunate that the creekside bank on our property is stable. It's about 40' high and 45-50 degrees slope. All covered with vegetation, 50+ year old trees, and decent leaf-litter mulch/loam surface. Underneath is sand, so it is potentially fragile if disturbed. Just a 1/2 mile downriver from me, the banks are still evolving. My friend had to spend $50K to cut his bank back to a stable angle and add rip-rap and hardwood mulch, along with shrub plantings.

Luckily this is a very stable hillside and the lake/pond area has no current or anything and is about 100' from where the base of the wall would be. The goal is to create a flat area with a well defined edge by the pool. There has been a small amount of shifting and the pool deck has sunk / settled a few inches. The edge of the pool deck to the drop off is less than 10' and probably 6 - 8' most of the way. I'd like to flatten it out and then use the retaining wall as a 'fence' for the pool. At the moment the pool isn't fenced (we're a long ways away from anywhere a person would wander in from). I'm trying to avoid either putting a fence down the hill (creates a very steep angle ending in a fence and someone or something will certainly get trapped). I'm also trying to avoid putting a fence across the current area and blocking the view, which is a sweeping view of the lake and kind of an 'infinity pool' look.

Will see if I can get a picture or two tomorrow.

 

[MikeInEburg]

Regarding Gabions, Macaferri has detailed installation documents on their web page. I think the cost for a 4×4×8 basket was $175.00 or so.

 

[Streetcar]

A pier wall would require large equipment and design by engineer. Depending on the height of the wall and zoning ,the wall may need designed. Most precast block walls have minimal footing width and depending on height, may be set by hand

 

[tractchores]

Height is an important piece I left out. Looking at something that's probably 2 - 4 feet most likely (based on the current grade and where I can put it without getting into a bunch of wetlands permits).

 

[CurlyDave]

Height is an important piece I left out. Looking at something that's probably 2 - 4 feet most likely (based on the current grade and where I can put it without getting into a bunch of wetlands permits).

Out here on the left coast (I have experience in both CA and OR) a wall 4' and under is a Landscape Wall and does not require engineering. Over 4' and it is a Retaining Wall which does require engineering and inspection. Get used to calling what you want to build a Landscape Wall and you will save Thou$ands in costs.

I have built walls up to about 6' using Keystone Block Retaining Walls | Keystone Retaining Wall Systems LLC. Allan Block Retaining Walls | Allan Block Wall Systems is another close alternative. There are other suppliers but these are the ones I have experience with.

Either of the blocks I mention have the huge advantage that they are small enough that individual pieces can be hand carried, so you do not need heavy equipment to place them. Your tractor would be helpful for earth moving, but not necessary for block placement.

I am not certain what you mean by "nose pressure", but it was not a concern with the Keystone Blocks. Overturning force (or, more properly overturning torque) was handled by burying the lowest course of blocks in the earth, sloping the wall backward from vertical (called batter in the literature) and installing geogrid at the appropriate levels of the wall.

Pictures and a diagram would be really helpful.

 

[Steve_Miller]

We started making these about three months ago and they are taking off like hot cakes. They were chosen for the small contractors because of their weight so that a small excavator or skidsteer could place them. We've made the bigger sister (Stone Strong we call them, weight about two tons or more a piece) for years now and they are very popular because they can be used, I think to hold back a wall up to thirty feet in height if installed correctly. Not sure if you need engineering for prove, but if no one inspects how would anyone know without a failure to prove shoty installation. The patent is from New Hampshire so they should be in your area or something to that effect I would guess.

Steve

 

[check]

What is the slope of the soil, Is the creek stabile or moving? Scour at toe of the wall can cause problems You will need some method to drain water behind wall

Stable or moving? Scour?

 

[Streetcar]

Stable or moving? Scour?

Does the water stay in a constant channels, is the bank covered with vegetation or eroding.
Scour is moving water eroding under a fixed structure

To OP for wall under four foot height go with precast block as curly Dave mentioned. Check building supply to see what is sold in your area. Both types that he mentioned are good products