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04-03-2017, 07:25 PM   #1
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How to calculate amount of fill dirt needed for slope

The fill area slopes in two directions. From zero fill on the left to 4 foot deep on the right side. Its 32 feet from left to right and 13 feet deep from front to back. Does there exist an online tool or formula that will allow me to get a reasonably accurate estimate for the yards of fill dirt needed? If it was a perfect cube, I understand I could multiply LxWxH to get the volume. So, since it slopes from zero, can I just divide the calculation by half to get the volume?

For that I get 32x13x4 = 1664
1664/2=832 cubic feet.
832/27=30 cubic yards

Does this sound right? If so, what would be a rought estimate of cost for 30 cubic yards of fill dirt delivered?

Last edited by homeimproverjoe; 04-03-2017 at 07:31 PM.

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04-03-2017, 09:58 PM   #2
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Re: How to calculate amount of fill dirt needed for slope

That's close to right, Math is sound, but now you need to allow for the fact that fill is loose material, so when you tamp it down you are going to need 10 to 25 % more. Depending on the fill you get and the looseness in it.

Are you going to install a retaining wall first, or at all?

ED

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04-04-2017, 06:41 AM   #3
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Re: How to calculate amount of fill dirt needed for slope

Quote:
 Originally Posted by de-nagorg Are you going to install a retaining wall first, or at all? ED
Thanks Ed. I'm strongly considering it. Along the right side, staggered from 4 foot where it meets the wall, down to zero 13 foot out from the wall where it meets the slope of the existing yard and creates the drainage path for runoff.

I found the cost of retaining wall notched pavers to be fairly economical.

I'm also considering just sloping the wall off to the right instead of using retaining wall. It would appear more natural but require much more fill dirt.

Last edited by homeimproverjoe; 04-04-2017 at 06:46 AM.

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04-04-2017, 07:02 AM   #4
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Re: How to calculate amount of fill dirt needed for slope

Quote:
 Originally Posted by de-nagorg That's close to right, Math is sound, but now you need to allow for the fact that fill is loose material, so when you tamp it down you are going to need 10 to 25 % more. Depending on the fill you get and the looseness in it.
To simplify the calculations, I used a perfect cube. However, the fill will only extend level about 4 feet from the wall (to form a level flower bed for plantings). It will then gently slope down to meet the existing reverse slope of the yard appx 13 feet from the wall. This will create a V shaped runoff path that will divert water to the right side of the house.

Based on that, I'm expecting I should have enough overage in the calcs to allow for tamping of the dirt.

Along those lines, I'm considering renting a Bobcat MT85 or MT55 to move the dirt from the dump site to the location. Can I tamp the dirt with the tracks or do I absolutely need a separate attachment or machine?

Last edited by homeimproverjoe; 04-04-2017 at 07:05 AM.

04-04-2017, 08:01 AM   #5
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Re: How to calculate amount of fill dirt needed for slope

What plans are there for erosion control?

If you don't plan now, all your work will be washes into the back yard, and lower area.

I would use some large rock in the base to keep water in control.

Those wall blocks are great to work with, a little heavy after a few hundred, but really stacks nice.

They need a solid foundation to be permanent, or they will slide away too.

Is there room to maneuver the Bobcat easily, it's gonna tear up ground turning around.

ED

04-06-2017, 07:09 AM   #6
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Re: How to calculate amount of fill dirt needed for slope

Quote:
 Originally Posted by de-nagorg What plans are there for erosion control?
The first 4 feet from the wall will be bedded plants with mulch beds. The remaining 9-10 feet of the ground will be sodded zoysia.

Quote:
 Originally Posted by de-nagorg I would use some large rock in the base to keep water in control.
Interesting. Do you mean gravel for drainage or boulders for mass/fill? I have some very large embedded rock/boulders on the rear of the property. Could pile some in the deepest part of the fill near the right rear section. For drainage, there will be dimpled waterproofing membrane attached to the wall with 30 feet of interconnected NDS 4-in x 10-ft Corrugated French Drain Pipe along the wall base for drainage out to the right side. https://www.lowes.com/pd/NDS-4-in-x-...n-Pipe/3136611

Quote:
 Originally Posted by de-nagorg Those wall blocks are great to work with, a little heavy after a few hundred, but really stacks nice. They need a solid foundation to be permanent, or they will slide away too.
By calcs, I need appx 120 blocks. For a base, plan is to level the wall base path twice as wide as the blocks with the first course below grade, then stack courses from there to form a pie shaped wall that goes from 4-6 foot at the wall down to zero 13 feet out in front at the drainage channel.

Quote:
 Originally Posted by de-nagorg Is there room to maneuver the Bobcat easily, it's gonna tear up ground turning around.
Should be. I have a skid steer guy coming by this week for a quote.

Last edited by homeimproverjoe; 04-06-2017 at 07:34 AM.

04-06-2017, 08:37 AM   #7
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Re: How to calculate amount of fill dirt needed for slope

That sounds like a good plan, and getting a local operator, engineer involved is great.

They will be better able to advise you on what will be best for your project, they have eyes on the slope, as well as knows how to run the bobcat, and do this to your expectations.

I was wondering if you were planning on using any waterproofing membrane on the basement wall, now I know that you are.

ED

04-06-2017, 10:43 AM   #8
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Re: How to calculate amount of fill dirt needed for slope

Just one thing that comes to this DIYer's mind. You might consider hiring someone with a bobcat as the cost of renting a bobcat and if not use to using one, renting may be near the same cost. Around here they charge by the hour as a rule.

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04-06-2017, 01:03 PM   #9
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Re: How to calculate amount of fill dirt needed for slope

Quote:
 Originally Posted by Mike Milam Just one thing that comes to this DIYer's mind. You might consider hiring someone with a bobcat as the cost of renting a bobcat and if not use to using one, renting may be near the same cost. Around here they charge by the hour as a rule.
Thanks Mike, I'm getting a few quotes from some local operators. The cost for a Dingo is \$209 a day from local Home Depot. Larger bobcat machines go for about \$300/day.

Going rate for skid steer guys here is \$60-\$75 an hour with \$250 minimum. I'd expect a skilled operator could get in and out in a few hours and do it right for about the same as a day's Bobcat rental.

Last edited by homeimproverjoe; 04-06-2017 at 01:11 PM.

04-06-2017, 01:06 PM   #10
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Re: How to calculate amount of fill dirt needed for slope

As well, the Bobcat operators might have a source of fill dirt and/or topsoils.
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04-07-2017, 08:51 PM   #11
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Re: How to calculate amount of fill dirt needed for slope

Quote:
 Originally Posted by jlhaslip As well, the Bobcat operators might have a source of fill dirt and/or topsoils.
Just met with the first guy and sure enough, he indicated that he could get fill dirt cheaper than my original quote. Estimated 4-8 hours for the complete grade and fill job.

04-09-2017, 08:25 AM   #12
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Re: How to calculate amount of fill dirt needed for slope

What's the objective?
A flower bed. Anything else?
That's a tremendous slope to alter and/ or a big force on whatever you build for a wall.
Is there a full basement behind that wall?
Could you get by with a flower bed that spans the center 1/3 of the wall? That may reduce your costs 80%.
I'd keep that tree at least 20' from the building. Trees and buildings don't get along very well. From roots and branches to rot and leaves on the roof, the greater the distance the better. You may want to consider 30' distance.
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04-09-2017, 08:57 AM   #13
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Re: How to calculate amount of fill dirt needed for slope

Hi Mike, it will just be a 3-4 foot bed for foundation shrubs under the windows. It will be level across the wall until the midpoint of the last window on the right where it will gradually slope down to grade on the right. I will plant monkey grass on the slope to hold the soil. The trees will be planted out in front of the monkey grass slope area. Pics below...

04-09-2017, 09:05 AM   #14
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Re: How to calculate amount of fill dirt needed for slope

How about some daylily/hemerocallis to REALLY hold the slope together....

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04-09-2017, 09:17 AM   #15
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Re: How to calculate amount of fill dirt needed for slope

Thanks for the suggestion and feedback. I chose the monkey grass b/c we already have lots of it growing in the area where the slope meets grade so I know it grows well in that area and is holding slope well currently.

There is also a considerable amount of it on the left side bed area where we will be excavating. It will have to come up so I was thinking to preserve it and transplant it over on the right side on that new slope.

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