View Full Version : wood mulch as fill...

Clarence Martin
07-24-2015, 4:30 PM
Got a portion of the side of my backyard that I need filled in. It's got a slope of I would say 45 to 60 Degrees, that slopes down to the wood fence. From the bottom of the fence to the top of the slope, I would estimate about 4 feet down. It's about 7 to 8 feet wide. and runs 15 to 20 feet in length.

Now , I could get dirt fill, but that is a lot of dirt fill . Neighbor is a tree trimmer , and gets 20 ton dump truck loads in all the time. I was thinking of getting a few of these loads , spread the mulch out where I need it filled in, and then get a load of dirt fill to spread over top the mulch. Then put grass seed on top of it.

Does this sound like a good idea, or is there a better way ?

Ryan Mooney
07-24-2015, 4:54 PM
Some possible downsides:

It will settle, perhaps substantially as the wood decomposes and compacts. This will be ongoing over some number of years. Odds are good that the settling will be uneven and you may perhaps have some small sink holes.

If it catches on fire it will be very difficult to put out and can burn for months. There is some small possibility of spontaneous combustion of large piles, especially if the wood is put in the ground when green/wet (https://www.extension.purdue.edu/extmedia/id/id-421-w.pdf see pages 2 and 3).

Having said that.. you might do better with unchipped wood as fill if you're willing to go for a more riparian or raised garden and less of a mowed lawn look - check out a google search for "hugelkultur" (you'll also get some good ideas of the settling rates from some of those sites).

Wade Lippman
07-24-2015, 5:07 PM
What exactly are you going to fill in? You can't just fill in a 60% slope without it sliding down unless you have a retaining wall.

Charlie Velasquez
07-24-2015, 6:11 PM
I figured about 270 cu.ft. of fill. What is on the other side of the fence?
Will the fence sustain a 4' difference in height?
As noted, wrt settling and decomposition.

Additionally, as the chips decompose it will affect the ph level and nitrogen content of the soil. I doubt the grass will do well for many years.

Clarence Martin
07-24-2015, 7:45 PM
1. Metal , chain link fence divides my backyard with the next door property.

2. Next door property is a vacant lot , that a few years ago used to slope WAY down! That was filled in with a LOT of dirt and heavy. hard road fill, when there was a major redo of the highway out front. They let that lot settle over all this time. It was recently sold. It was assessed for 7500 with a full market value of 8500. It sold for $2000

3. I don't think it will sell , even though it is on the market . Need a full basement per Town Code and would have to have a Septic System and a Well drilled. How they would be able to do that, with all the Concrete, brick , steel and cast Iron pipes, Black Top rock and dirt, ect , that was dumped as fill, I don't know .

4. As for the difference in height and settling, I was not thinking of bringing it up to level height, just put in enough fill , to ease the angle of the slope , so that I can mow the lawn easier without the tractor tipping.

Ole Anderson
07-24-2015, 8:11 PM
If it is eight feet wide and four feet tall, then sloped out would result in a 1v:2h slope. Still much too steep for a tractor. I wouldn't recommend chips due to settling and being left with a "spongy" base to ride the tractor on. 270 cf (if correct)= 10 cubic yards, or one tandem axle dump truck.

K. L. McReynolds
07-24-2015, 9:07 PM
You do not want walnut chips in the mulch. Walnut roots have toxins to other plants.

As said previously, the chips take a long time to decay if just left. The mulch has to be turned periodically to become useful in a year or so.

There will be settling and movement until the mulch has become dirt. The chips can develop fungus/disease and become really problematic, especially wet(live when chipped) mulch.

The overfilled dirt could dissolve into the chips with several rains.

I worked for a local utility for 22+ years, much of it repairing tree trimming equipment(saws/chipp0pers/hydraulic trucks and equipment). I had to recover a small tracked dozer used to spread the chips(from 11 trucks dumping two loads a day) when the dozer got stuck in the chip pile(about half an acre). That pile started on old chips(the pile was used for 10+ years---extending out into a huge gully). So after ten years, the first loads(being driven over 22+ times a day, five days a week, 50 weeks a year) were still chips and had not become completely dirt.

Now, having said all that, I just had a sweet gum dropped in my back yard, and the stump ground. Most of the chips went back into the hole. I turn the top and water it(when it does not rain). Been three months and the top layer is still chips.