Newbie question about retention walls

[Swampa]

Hi everyone,

First time here and first post but love your site after spending the morning on it!

Here goes:
I've been brought in to bid on building a retention wall around a new pond that's under construction. Finished pond will be 1.5 ish acres. The goal is to build a 10' boardwalk out of pavers around the pond. On the inside of the boardwalk (pond side), they asked if we could build a retention wall to be finished under water so that it would serve as a wall for my boardwalk to build off of. If we go this route the concrete blocks would be submerged almost 2' year round. The blocks are heavier duty than HD blocks, they are old castle with a rough finish. Link is attached to see the blocks we have to use.

My question is: Will the wall last underwater like this? I can pour a footer if needed.

Pavestone Regal Stone Pro 18 in. W x 12 in. L x 8 in. H Rock Face Pewter Blend Concrete Wall Block (36-Pieces/36 Face Ft/Plt) 81800 - The Home Depot

A full 1 sq. ft. face complemented by a natural texture makes the Regal Stone Pro RockFace a beautiful addition to any landscape. Behind the handsome, rugged exterior is a hollow core that lightens the

www.homedepot.com

Thanks,
Coby

 

[j.w]

@Swampa
I'll leave this question for someone in the know

 

[addy1]

Welcome to the forum!

 

[Mmathis]

Hello and welcome! Sounds like a big project!

 

[GBBUDD]

Some of the so called retaining wall blocks are lightweight concrete with low compression strengths coming from the depot odds are better that they may just be as I mentioned but can't say for sure. So it depends is this wall only to support the walk and not any water? Is the walk going to be gravel process, papers or wood?
I imagine this is an earthen pond base if so odds are it's going to have a week sloppy base/bottom that's bto be your fight , yes your base footing is crucial if it's not sitting on solid ground.
The different techniques are to nu.urous to get into without more info. A foot or more of gravel in a trench, mafia blocks, poured concrete to name a few

Also is this wall 3 feet tall or 6 feet

 

[hammer]

We design this kind of stuff professionally with structural engineers all the time and we never use modular block to do it because typically you don't want water behind the wall and that is what you will get with modular block unless you use a liner and thats impractical at that scale but technically do-able. We pour concrete walls, I have one being built in Taunton, MA this year.... I'd put the whole boardwalk on piers and then put modified rip-rap (8" minus broken stone) and make a 2:1 slope starting just inward of the boardwalk face so that you can't see the slope starting and have the ground meet the other side of the boardwalk. The boardwalk should be 2' about mean average high water or it'll rot regardless of the treatment you use, UNLESS it's IPE or the like. short answer, I wouldn't use the block. I'm a licensed landscape architect and surrounded by 100+ civil engineers, which doesn't mean my answer is the best or the only one, i'm just offering what I'd do is all... it's one thing to do a-b-c- at our own houses, it changes when it's somebody else.

on temporary inundation like detention basins, we've used modular block.... I'm sure you could make it work with the right stone behind the wall but it's a risk.

 

[Swampa]

Thanks for the responses. More clarity, the pond have a liner. The retention wall is for erosion as the slope is pretty steep. Also, the retention wall will basically serve as a border for my travertine paver boardwalk. I've since learned, that we will also build another retention wall behind my boardwalk.

 

[hammer]

if the pond has a liner, the wall has the correct batter, and you backfill it correctly, and fill the block openings with rebar and concrete it’ll work.