Turning an Old Crawlspace Foundation Into a Pond

[SpryNotI]

I am thinking about buying a piece of property that has an old crawlspace foundation. The foundation is made out of cinder block, it is about 20x32 feet, about 18-20 inches above ground, i believe it has a footer that hopefully is below frost line. It has two smaller (10x12 & 8x8 ft) rooms in diagonally opposed corners. I might be able to dig the interior deeper. I was planning to line this with pond liner, which I may be able to get for free, and place dirt and boulders around the exterior. I also plan to fill any voids in the cinder block with concrete. I planned to use the 8x8 room as my filter and the 10x12 room as a bog. I also have a number of preformed ponds that I will incorporate into the design.

Will the pressure of the water be too much for the cinder block walls even with the dirt and boulders on the exterior giving them some support?
Anyone have some links for DIY pond filters that can go into the 8x8ft room?
Should I just turn it into a raised bed garden?
Should I just bite the bullet and tear it out?

 

[Lisak1]

Wow! Interesting concept. Whether or not it "holds water" so to speak depends a lot on how those cinder block walls were constructed and how well they've held up over the years. Quite honestly, it may be less work to just start from scratch but that's a personal choice.

Welcome to the GPF!

 

[Sparky]

I love the idea! So many options. But in my mind yes I think it would work. Are the top cinders filled?

 

[MajorDan]

I would backfill to about 3-4” of top of block walls to give them added support for the lateral forces water will put on them.

Looks like a great project. If you dig the inside deeper leave a good sized shelf around the inside to avoid the footers and dig as deep as you like.

As a warning though, block walks are not designed for lateral (sideways) loads so the backfill around the walls is important. You can also lower the lateral load by filling inside the walls and sloping the fill from about half way up the wall. Think of the walls as the middle of an earthen damn with dirt sloping away on both sides. Hope this explanation makes sense.

 

[j.w]

@SpryNotI Sounds like an interesting project. Hope you post photo's and let us watch what you do.

 

[SpryNotI]

Appreciate all the replies.

Some of the cinder blocks have concrete in them some do not. If I do this I will fill all of them.

Leaving the shelf is a good idea and serves more than one purpose. I needed to make sure I construct something ramp-like in a few places to allow turtles to escape. Don't plan to stock turtles but this is in a rural area so I'm sure some will show up.

I may construct buttresses against the the walls on the outside in addition to the back-fill.

 

[addy1]

Welcome to our group. This sounds like a neat project.

 

[poconojoe]

Sounds great! I think the idea of filling the blocks with concrete and supporting the walls with soil are good ones. And you can't go wrong with some sort of buttress support under that soil. I was thinking that maybe you could drive some rebar down through the voids in the block before you fill them with concrete. I don't know if they would go very far if there was indeed a concrete footer under there. But it was a thought...
I would definitely dig deeper. 18"-20" is not deep enough. Especially if you are in an area that freezes in the winter.
And your getting a free liner? How do I get that? LOL!

 

[sissy]

My pond is cinder block above ground by just over 2 feet and all I filled the block with is clay and rebar and I have had no problems with it .The tallest side I have an outside retaining wall block with rocks inside of it ,between the concrete block and liner .My pond is on a sloped hill so other side is closer to the sidewalk .I also put loose lay solid block ontop of the cinder block and no problems with that either .You can see some of it in my build sight .After I was done is when i pulled the liner up and added the cap block ,2 layers of it .

 

[sissy]

took some pics to show .But I would guess since we do not have heavy freezes here it works .The retaining wall block is 2 levels below the ground in first pic .The second pic is the other side of the pond near the side walk .i use foam insulation to protect the liner .

 

[GBBUDD]

If you are in an area that has frost /snow you really should answer the question of how deep does the wall go and does it have a footing . without these questions answered your rolling the dice on your hard work. And like poconojoe said rebar can be placed in the open bays before you pour the concrete in It would be best to set the rebar into the footing if at all possible for maximum strength. www.gardenpondforum.com/threads/going-for-it-phase-one-12-000-gallon-pond.22563/page-6