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I am planning soon to tear down an extensive retaining wall made of cement. The plan is to use the cement as fill and then to put about 2 foot of quality top soil on top to create a backyard where I plan to not grow a standard grass lawn, but rather to create a thyme & steppable lawn, and to plant flowers, shrubs, herbs & vegetables. There is excellent quality fill in place now and my concern is whether the cement can be broken into small enough chunks to still allow drainage, and whether the cement will leach and create an unhealthy soil ph, etc. Anyone have knowledge and advice to offer? I would much rather rid of the cement, but I need the additional fill. Thank you.
I'm not sure I understand why you need the cement as fill--you'd be better off filling it with dirt, I think your garden will be much better off in the long run if the area is filled up with dirt rather than having concrete chunks underneath it.
We live in a 30 year old house where "builders' debris", including
broken concrete, cinder blocks and rocks were used as fill in most
areas of our large yard, topped with several feet of soil. As time passed,
the soil has worn thin or washed out, and it is difficult to grow anything.
Plants and bushes never achieve good size because it's a struggle for
them to establish a deep root system in and amongst the buried debris.
Drainage is always rather poor as well.
If you must use the cement debris as fill for cost reasons, perhaps you
can consider adding raised beds for flowers and vegetables?
Thank you for replying. It is the sheer volume of the cement and its local that causes us to not want to try to remove it all. Also, there is a need for lots of fill and that can be expensive or unavailable. My question is whether I will beable to have successful plantings on top of it, with the use of approximately 2' of quality top soil on top.
June in New Mexico. Thank you for your reply. You have experienced what I have feared could be true. I love your city and state and know that it is a challenge to grow the typical garden there, but I love the native plants that do thrive there beneath the Sandias.
I've heard of other people who've been in similar situations to June where there's a bunch of junk under their soil and they had problems as well, that's why I think you'd be better off if you can put dirt in there instead, you'll definitely be better off in the long run. Can you post some pictures showing what you're trying to do? Maybe people could have some other ideas to help you. My mental picture of what you're doing is tearing down the retaining wall then filling in the area in front of where it used to be with dirt to bring everything up to the level where the retaining wall used to be. If this is the case, you could probably leave the retaining wall in place and fill in with dirt in front of it to make everything level, then when you plant as things fill in, they'll cover up the top of the retaining wall so you won't even notice it anymore. That saves you the trouble of removing the wall and also the issues of disposing of the cement.
To ecrane3, this retaining wall was originally over 11 feet high. We are only removing the top 4 feet, but it is still a very extensive wall. I have found a place for disposal and will beable to haul away some of the cement, but I'm afraid much of it will need to remain. I don't have time to post photos, my apologies. We have brought in at least 7 foot of quality fill up to this point. Has anyone out there had a "not so bad" experience with having concrete under topsoil? Thanks again.
Better to be slightly sorry than totally. Only 2 ft of dirt on top of cement would appear to be not enough. The more I think about it ... the less I like it. I have a bare cement piece bald spot in my lawn ... a chunk of cement someone buried ... not quite well enough. I'm gonna have to dig it out or hit it with a sledge hammer ... chain gang style. Your entire community is built on hills around the Umatilla River? The retaining wall ... standard. I used to live in Walla Walla so I've been to or thru Pendelton hundreds of times.
For it to work you'd need to fill the voids w/ rough gravel not dirt or sand.
Then put some kind of landscape cloth over it.
Then the dirt.
Otherwise it will pack soild...
We have a gravel driveway buried on our property and it's 'like' concrete.
Never drains...
2' of dirt is enough for most perennials... but not shrubs or trees.
Could you do some open 'pockets' straight to the original dirt for them?
I lived in a house where much of the yard was built over concrete fill and it wasn't good - but it was in a thirty-year floodplain and probably nothing like your situation, tarodreamer. I'd try to talk to someone like a civil engineer in your area and see what they say. Or maybe building inspectors... If you have freeze-and-thaw cycles there, the concrete will come to the surface eventually, but there may be a depth (frost line?) where that isn't the case.
Spruces (black, white, red) will grow to utility pole size and bigger in a foot of soil on top of solid bedrock. I had a yard full of them in Maine. You could barely get a shovel in the ground without a clang and hurting your foot.
Thank you all for your replies. I think I will insist that we haul away absolutely as much cement as possible. Meanwhile, I'm looking forward to the remodel! I appreciate your experiences and sharing them with me.
