Pond behind retaining wall

[Greg]

My street was cut from the side of a hill, so my back yard is level for about 20 yards, then shoots up at about 30-45 degrees well into my backyard neighbor's yard. I am putting a retaining wall into the slope to have a pond, half walled by the retaining wall and half walled by the rising slope of the ground.

My question relates to the flexible liner for the pond, and how to connect the liner and the retaining wall. My working assumption is to trim the edge of the liner so there is a little (2-3") lip that will rest on the top of the retaining wall. The wall blocks are about 10" deep, so I would have 8" of reatining wall top free and clear. I would glue the underside of the liner to the top of the retaining wall, then glue the retaining wall caps on top of that. The retaining wall blocks and caps are concrete (Country Manor). Any problem with that idea? I presume I can call the liner manufacturer when I buy it to find out the appropriate adhesive to use on the liner-wall connection, and I would use standard landscape adhesive on the retaining wall-cap connection. Caps are 3" high, so the pond water level would be at least 3" below the top of the caps. The liner would lay against the sloping (up) ground and I would use large layered stone as the "cap" on that side.

sound right?

[Joe]

e Ought to work. Before proceeding, though, it might be a good idea to check and see of you need a building permit and what other restrictions might apply. Consider effects of major rainfall, for example, and what happens when the pond overflpws or (heaven forbid) fails. Have a good plan and you'll get good results

Joe

[RickH]

How high does the wall need to be on the low side of the hill for the depth and width of pond you want to dig? Ten inch interlocking landscape blocks with no other support may not be enough to hold back the water. Ponds on hillsides pose a lot of issues not encountered with level ponds. How much hill will still be above the pond generating runoff and more groundwater that will flow and scoot under your liner? I strongly suggest you cut bottom drain in this pond with a bulkhead and valve that exits below the wall, and lay sand. That hill will generate water flowage under your liner and that water will flow under your retaining wall undermining that too. Three inches of overlap on the edges is not enough in my experience even for a level pond. Because of that hill and water running under the liner/wall you are going to have to "overbuild" everything and come up with a drainage plan to not undermine the walll nor "float" the liner.

[Cam in Toronto]

Why glue it? I have a similar pond. The EPDM liner lays over the top of the last course of blocks and is held down by the cap stones. If you glue and the liner pulls as the pond settles you could tear the liner.

[dss]

Greg,

I also have a similar pond built into a hill. The retaining wall is six courses of about 5" blocks and the liner is held down by 2" caps with no glue. I'm in Minnesota so the blocks tend to move as the ground freezes and glue on the liner would be a problem. Go with as much liner overlap as your caps will allow and you'll be fine.

I put a beach into the hill-side of the pond and the birds love it. Ten years plus and everything is fine. If you can engineer a bottom drain that would be good.

dss

[hallerb]

all retaining walls fail sooner or later, if yours is holding back enough water to damage your home or others, be very careful. your insurance may not cover your loss.

retaing wall must have footer below frost line. i would consult a engineer, so you dont have future troubles, either because of a disaster, or a problem at home resale time.

my mother and step dad # 2 had a execvation done for a car parking area, that later was blamed for a small landslide, that endangered a neighbors home.

engineering and legal fees cost 5 grand......

dont put yourself in a similiar situation:(