is my pond construction safe?

[ashley bennett]

hello all,

please bear with me as I'm new to all of this, I've never had a pond or built one but would like to have one.

myself and my wife recently moved into our house now and in the back garden there seems to be a half built pond, as I've always wanted a koi pond we were looking into finishing it off. now we are planning on having a rear extension built we are a bit concerned if the walls are strong enough the last thing we want is to finish our extension and the pond wall gives way and floods the new extension.

a few details about it - it measure 6800mm (22ft 4") long and 3000mm (9ft 10") wide, measurements taken from outside point of blockwork. it is approx. 5ft deep all over. as the garden is slightly sloped the end closest to my house is out of the ground by approx. 3ft and the far end is out of the ground by approx. 2ft. footings seem to be approx. 18" deep from what I can see on the inside of pond. and its build from concrete blocks lead flat. and the longest side runs up the boundary line to next door.

I've tried looking on google for how much pressure will be on the wall and got a bit confused so hoping someone can help me with working out if the walls are safe and will not collapse when / if finished. if it is not strong enough is there any easy / cheap ways of making it stronger? as if it is unsafe and I need to knock it down I'm not sure I will have the funds left to build from scratch so will prob have to fill it in which I would prefer not too.

I've uploaded some photos to try and help / explain I know it looks tatty but I was told they planned to render it at the end.

thank you in advance for any help

 

[sissy]

great info you added to your post .Are you planning on putting a liner in it .You can also coat the inside of the block work and then install a liner to feel safer .It looks well built to me ,no expert on concrete work and your weather conditions

 

[ashley bennett]

great info you added to your post .Are you planning on putting a liner in it .You can also coat the inside of the block work and then install a liner to feel safer .It looks well built to me ,no expert on concrete work and your weather conditions

hello, I was planning on using a liner, I'm in the uk so weather is pretty mild, I was more concerned about the one end weather blocks lead flat 3ft high was strong enough as id imagine there is a lot of pressure coming from the water in pond. thanks for your fast reply

 

[Nepen]

my old brick raised pond was quite strong (and I laid it myself) I think people used landscaping timber / timber to build rasied pond successfully so I think concrete blocks should be fine

 

[sissy]

All 4 inside parts have block so guessing they just wanted extra support at that end just in case

 

[ashley bennett]

All 4 inside parts have block so guessing they just wanted extra support at that end just in case

hello sissy, sorry I'm not sure I know what you mean? thanks ashley

 

[PondMutt]

these are engineering questions ... quite a real concern , the sidewall of the pond blowing out .. .. let me get my sliderule and figure it out .. oops lost track of the sliderule about 30 years ago..

notice on the lower end of the containment where the flagstones are laid there is a wood frame started ...
just guessing , maybe , if you framed on around and bermed dirt up maybe,,

solid block like i see has good compression strength but the shear strength is a question
..
who here can calculate the pressure on the sidewall , assuming 5 foot of water ,, the lower you go ,, the more ,, umm .. i should be able to calculate this ... or maybe not
5 foot of water will put quite a lot of pressure on the side wall //
solid frame or berm dirt is my wag [wild ass guess]

 

[ashley bennett]

these are engineering questions ... quite a real concern , the sidewall of the pond blowing out .. .. let me get my sliderule and figure it out .. oops lost track of the sliderule about 30 years ago..

notice on the lower end of the containment where the flagstones are laid there is a wood frame started ...
just guessing , maybe , if you framed on around and bermed dirt up maybe,,

solid block like i see has good compression strength but the shear strength is a question
..
who here can calculate the pressure on the sidewall , assuming 5 foot of water ,, the lower you go ,, the more ,, umm .. i should be able to calculate this ... or maybe not
5 foot of water will put quite a lot of pressure on the side wall //
solid frame or berm dirt is my wag [wild ass guess]

hello pond mutt,
thank you for your in put, the wood around the bottom on the one picture was me I was going to put decking down but have changed my mind to slabs so the wood has nothing to do with the pond.
another option I have thought of is if I was having a pond I would of preferred a shallower end somewhere so I was thinking if I built a wall say a 3rd of the way in from the highest wall end and built it up so there was a remaining depth of say 2 ft then filled in the hole, would that reomove some of the pressure as there would only be 2ft supported by concrete blocks lead on there side the rest would have 2 concrete block walls and 6ft of what every I fill it with.
that way I would have a 1/3 of the pond at a depth of 2ft ish and 2/3 of the pond at 5ft.

hope that makes sense lol

thanks again
ashley